Method and apparatus for data transfer using a time division multiple frequency scheme supplemented with polarity modulation

ABSTRACT

A method of data transmission according to one embodiment of the invention includes encoding a set of data values to produce a corresponding series of ordered n-tuples. The method also includes transmitting, according to the series of ordered n-tuples, a plurality of bursts over a plurality n of frequency bands. Specifically, for each of the plurality of bursts, a frequency band occupied by the burst is indicated by the order within its n-tuple of an element corresponding to the burst. A bandwidth of at least one of the plurality of bursts is at least two percent of the center frequency of the burst. Information is encoded into a polarity of at least one of the plurality of bursts.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/372,075, filed Feb. 20, 2003 , which is a continuation-in-part (CIP)of both of (1) U.S. patent application Ser. No. 10/255,111 filed Sep.26, 2002, now U.S. Pat. No. 6,895,059 and (2) U.S. patent applicationSer. No. 10/255,103 filed Sep. 26, 2002, now U.S. Pat. No. 6,781,470 ,both of which claim priority to U.S. Provisional Patent Application No.60/326,093 filed Sep. 26, 2001 , the entirety of all of whichapplications are incorporated herein by reference.

U.S. application Ser. No. 10/372,075, filed Feb. 20, 2003 also claimspriority to U.S. Provisional Patent Applications Nos.: (1) 60/359,044filed Feb. 20, 2002 ; (2) 60/359,045 filed Feb. 20, 2002 ; (3)60/359,064 filed Feb. 20, 2002 ; (4) 60/359,147 filed Feb. 20, 2002 ;(5) 60/359,094 filed Feb. 20, 2002 ; (6) 60/359,095 filed Feb. 20, 2002; and (7) 60/359,046 filed Feb. 20, 2002 ; all of which applications areincorporated in their entirety herein by reference.

This application is related to the following U.S. patent applications,all of which are incorporated in their entirety herein by reference:U.S. patent application Ser. No. 10/372,065 filed Feb. 20, 2003 ; U.S.patent application Ser. No. 10/371,799 filed Feb. 20, 2003, now U.S.Pat. No. 7,236,464 ; U.S. patent application Ser. No. 10/371,064 filedFeb. 20, 2003 ; U.S. patent application Ser. No. 10/371,074 filed Feb.20, 2003 ; and U.S. patent application Ser. No. 11/131,826 filed May 17,2005.

BACKGROUND

1. Field of the Invention

This invention relates to data transfer over wired, wireless, and/oroptical transmission channels.

2. Background Information

As computing and communications applications become richer and morecomplex, it becomes desirable to support transfers of data betweendevices at higher and higher rates. The increasing popularity ofconsumer electronics, computing, and communicating devices, in variousforms (e.g. mobile, hand-held, wearable, and fixed) and possibly withassociated peripherals, indicates a clear demand for these types ofdevices and for connectivity (e.g. peer-to-peer and/or networked)between them. Unfortunately, present-day communications technologiesfall short of providing the technical requirements necessary to supportsuch demands.

Wireless connectivity may enable greater user experiences and possiblyspur an increased demand for such devices. For example, wirelessconnectivity can provide enhanced capability; is expected to be easierto use; may encompass cost savings and increases in efficiency andproductivity; and may increase possible device applications and/ordeployments.

Use of such devices may include large data transfers and/or multimediaapplications. For example, a cable replacement scenario for a computer,a consumer electronics device, or a similar device may need to supporttransfers of large amounts of data. Multimedia applications may handlemultiple simultaneous streams of high-definition audio and/or videocoming from devices such as business/entertainment systems and gateways.

Most existing wireless schemes transfer data via modulatedcontinuous-wave carriers. In many cases, a portion of theradio-frequency spectrum is reserved for the exclusive use of thescheme. Such reservations allow these transfer schemes (e.g. commercialradio and TV broadcasts) to operate free of interference from otherdevices and without interfering with other systems.

Data transfers may be conducted over very narrow frequency bands in anattempt to occupy less of the frequency spectrum. However, such schemesmay be more susceptible to increases in background noise level and tomultipath interference. Some narrowband schemes may also be more likelyto interfere with other systems (e.g. due to a higher concentration ofenergy in the particular frequency band being used).

Although battery technology is steadily improving, operating timesbetween charges or replacement are still important factors in the designof portable devices. Complexity and cost of transmitter and receiverimplementations are other important factors for consumer applications.Present-day solutions offer only a few of the necessary technicalrequirements. For example, some may provide low cost and low powerconsumption but only at low bit rate, while others may have higher bitrates but be unacceptable in terms of cost and/or rate of powerconsumption.

It is desirable to support high rates of data transfer. It may also bedesirable for a scheme that supports high, medium, and/or low rates ofdata transfer to obtain one or more advantages such as 1) low powerconsumption, 2) low cost of implementation, and/or 3) an ability tocoexist with interferers and/or with other frequency use. Otherdesirable advantages may include scalability with potential capabilityfor backwards compatibility and/or an ability to determine positionand/or location.

SUMMARY OF THE INVENTION

A method of data transmission according to one embodiment of theinvention includes transmitting a plurality of bursts, each burstoccupying one of a plurality of frequency bands. At least an order oftransmission of the plurality of bursts in time and a polarity of atleast one of the plurality of bursts encodes a symbol, the symbolcorresponding to a plurality of data values. Additionally, a bandwidthof at least one of the plurality of bursts is at least two percent ofthe center frequency of the burst

A method of data transmission according to one embodiment of theinvention includes encoding a set of data values to produce acorresponding series of ordered n-tuples. The method also includestransmitting, according to the series of ordered n-tuples, a pluralityof bursts over a plurality n of frequency bands. Specifically, for eachof the plurality of bursts, a frequency band occupied by the burst isindicated by the order within its n-tuple of an element corresponding tothe burst. A bandwidth of at least one of the plurality of bursts is atleast two percent of the center frequency of the burst. Information isencoded into a polarity of at least one of the plurality of bursts.

A transmitter according to another embodiment of the invention includes:an encoder configured to receive an ordered set of m data values and toproduce a corresponding series of ordered n-tuples; and a signalgenerator configured to transmit, according to the series of orderedn-tuples, a plurality of bursts, each burst occupying at least one of aplurality n of frequency bands. For each of the plurality of bursts, afrequency band occupied by the burst is indicated by the order withinits n-tuple of an element corresponding to the burst, and a bandwidth ofat least one of the plurality of bursts is at least two percent of thecenter frequency of the burst. The transmitter is configured to encodeinformation into a polarity of at least one of the plurality of bursts.

A method of data reception according to a further embodiment comprisingthe steps of: receiving a plurality of bursts, each burst occupying atleast one of a plurality n of frequency bands, wherein information isencoded into a polarity of at least one of the plurality of bursts;obtaining a series of ordered n-tuples based on the plurality of bursts;and decoding the series of ordered n-tuples to produce an ordered set ofm data values. For each of the plurality of bursts, the order within itsn-tuple of an element corresponding to the burst is indicated by afrequency band occupied by the burst, and a bandwidth of at least one ofthe plurality of bursts is at least two percent of the center frequencyof the burst. Information is decoded from the polarity encoded into atleast one of the plurality of bursts.

A receiver according to a further embodiment including a signal detectorconfigured to receive a signal including a plurality of bursts, whereininformation is encoded into a polarity of at least one of the pluralityof bursts, each burst occupying at least one of a plurality n offrequency bands, and to output a series of ordered n-tuples based on theplurality of bursts. The receiver further includes a decoder configuredto produce an ordered set of m data values from the series of orderedn-tuples. The signal detector is configured to output, for each of theplurality of bursts, an element corresponding to the burst such that anorder of the element within its n-tuple corresponds to a frequency bandoccupied by the burst. A bandwidth of at least one of the plurality ofbursts is at least two percent of the center frequency of the burst andthe signal detector is configured to output the information based uponthe polarity of at least one of the plurality of bursts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows examples of three ultra-wideband bursts at differentfrequencies.

FIG. 2 shows the three bursts of FIG. 1 in the frequency domain.

FIG. 3 shows a timing diagram.

FIG. 4 shows a timing diagram.

FIG. 5 shows a sequence of three ultra-wideband bursts in time.

FIG. 6 shows the sequence of FIG. 5 in the frequency domain.

FIG. 7 shows a time-domain plot of overlapping ultra-wideband bursts.

FIG. 8 shows a flowchart of a method according to an embodiment of theinvention.

FIG. 9 shows one example of an ordered set of m data values and acorresponding series of ordered n-tuples.

FIG. 10 shows a representation of one correspondence between an encodedsymbol and burst activity over time slots and across different frequencybands for the series of FIG. 9.

FIG. 11 shows another representation of a correspondence between encodedsymbols and burst activity over time slots and across differentfrequency bands.

FIG. 12 shows a diagram of an application in which bursts in differentfrequency bands are transmitted at different times.

FIG. 13 shows an effect of random time perturbation in clustertransmission start time.

FIG. 13A shows a cluster including a sequence of bursts in time withpolarity modulation to encode additional information into the cluster.

FIG. 13B shows two clusters of bursts, the bursts of the second clusterhaving a different polarity relative to the bursts of the first cluster.

FIG. 13C shows a cluster including a sequence of bursts in time withamplitude modulation to encode additional information into the cluster.

FIG. 13D shows two clusters of bursts, the bursts of the second clusterhaving a different amplitude relative to the bursts of the firstcluster.

FIG. 13E shows a cluster including a sequence of bursts in time withpolarization modulation to encode additional information into thecluster.

FIG. 13F shows two clusters of bursts, the bursts of the second clusterhaving a different polarization relative to the bursts of the firstcluster.

FIG. 13G shows a cluster including a sequence of bursts in time withwidth modulation to encode additional information into the cluster.

FIG. 14 shows an example of a scheme in which symbols for two differentlogical channels are transmitted over the same physical channel atdifferent times.

FIG. 15 shows an example of a scheme in which symbols for two differentlogical channels are transmitted over the same physical channel at thesame time.

FIG. 16 shows a block diagram of a transmitter 100 according to anembodiment of the invention.

FIG. 17 shows a block diagram of an implementation 150 of transmitter100.

FIG. 18 shows a block diagram of an implementation 110 of transmitter100.

FIG. 19 shows a block diagram of an implementation 410 of serializer400.

FIG. 20 shows a block diagram of an implementation 420 of serializer400.

FIG. 21 shows a block diagram of an implementation 120 of transmitter100.

FIG. 22 shows a block diagram of an implementation 222 of encoder 220.

FIG. 23 shows an implementation 302 of signal generator 300.

FIG. 24 shows trigger pulses on N independent trigger signals asgenerated by trigger generator 320.

FIG. 25 shows a block diagram of signal generator 302 and animplementation 452 of signal launcher 450.

FIG. 26 shows a block diagram of an implementation 303 of signalgenerator 302.

FIG. 26A shows a block diagram of one implementation of a signalgenerator for generating signaling having an additional modulation, suchas polarity, amplitude and/or width modulation, on a burst-wise orcluster-wise basis.

FIG. 26B shows a block diagram of a variation of the signal generator ofFIG. 26A.

FIG. 27 shows an implementation 304 of signal generator 300.

FIG. 28 shows a block diagram of signal generator 304 and animplementation 454 of signal launcher 450.

FIG. 29 shows a block diagram of signal generator 306 and animplementation 456 of signal launcher 450.

FIG. 29A shows a block diagram another implementation of the signalgenerator for generating signaling having an additional modulation, suchas polarity, amplitude and width modulation, on a burst-wise orcluster-wise basis.

FIG. 29B shows a block diagram of yet another implementation of a signalgenerator for generating signaling having an additional modulation on aburst-wise or cluster-wise basis.

FIG. 30 shows a block diagram of an implementation of a signal generatorfor generating signaling having an additional modulation on acluster-wise basis.

FIG. 30A shows an implementation of the modulator of FIG. 30 as apolarity converter for providing polarity modulation.

FIG. 31 shows an implementation of a transmitter for generatingsignaling having polarization modulation on a burst-wise or cluster-wisebasis.

FIG. 31A shows another implementation of a transmitter for generatingsignaling having polarization modulation on a burst-wise or cluster-wisebasis.

FIG. 31B shows yet another implementation of a transmitter forgenerating signaling having polarization modulation on a burst-wise orcluster-wise basis.

FIG. 31C shows an implementation of a transmitter for generatingsignaling having polarization modulation on a cluster-wise basis.

FIG. 31D shows an implementation of a transmitter for generatingsignaling having polarization modulation on a cluster-wise basis.

FIG. 32 shows a correspondence between waveform profiles in the time andfrequency domains.

FIG. 32A shows a spectral plot of a sequence of bursts.

FIG. 32B shows a spectral plot of a sequence of bursts.

FIG. 33 shows a block diagram of an oscillator 342 according to anembodiment of the invention.

FIG. 34 shows a block diagram of an implementation 344 of oscillator342.

FIG. 35 shows a block diagram of an implementation 346 of oscillator342.

FIG. 36 shows a block diagram of an implementation 348 of oscillator342.

FIG. 37 shows a block diagram of an implementation 350 of oscillator342.

FIG. 38 shows a block diagram of an implementation 352 of oscillator342.

FIG. 39 shows a block diagram of an implementation 356 of oscillator 342and a compensation mechanism 495.

FIG. 40 shows a block diagram of an implementation 358 of oscillator 342and an implementation 496 of compensation mechanism 495.

FIG. 41 shows a block diagram of oscillator 358 and an implementation498 of compensation mechanism 495.

FIG. 42 shows a block diagram of an implementation 354 of oscillator342.

FIG. 43 shows a block diagram of an implementation 360 of oscillator 342according to an embodiment of the invention.

FIG. 44 shows a block diagram of a receiver 400 according to anembodiment of the invention.

FIG. 45 shows a block diagram of a burst detector.

FIG. 46 shows a block diagram of an implementation 455 a of edgedetector 455.

FIG. 47 shows a block diagram of an implementation 532 of ADC 530 thatincludes a comparator.

FIG. 48 shows a block diagram of a receiver 401 according to anembodiment of the invention including an implementation 413 of signaldetector 410.

FIG. 49 shows a block diagram of an implementation 455 b of edgedetector 455.

FIG. 50 shows a block diagram of a receiver 402 according to anembodiment of the invention including an implementation 414 of signaldetector 410.

FIG. 51 shows a block diagram of a receiver 403 according to anembodiment of the invention.

FIG. 52 shows a block diagram of a receiver 404 according to anembodiment of the invention.

FIG. 53 shows a block diagram of a receiver 405 according to anembodiment of the invention.

FIG. 54 shows a block diagram of a receiver 406 according to anembodiment of the invention.

FIG. 55 shows a block diagram of a receiver 407 according to anembodiment of the invention.

FIG. 56 shows a block diagram of a receiver 408 according to anembodiment of the invention.

FIG. 57 shows a block diagram of a receiver 409 according to anembodiment of the invention.

FIG. 58 shows a block diagram of a receiver 409 a according to anembodiment of the invention.

FIG. 59 shows examples of several bursts and their center frequencies.

FIG. 60 shows an implementation of a receiver for receiving signalingincluding polarization modulation.

FIG. 61 shows another implementation of a receiver for receivingsignaling including polarization modulation.

FIG. 62 shows yet another implementation of a receiver for receivingsignaling including polarization modulation.

FIG. 63 shows a block diagram of a multi-band transmitter.

FIG. 64 shows a block diagram of a multi-band receiver.

FIG. 65 shows an embodiment of a trigger generator using an encoder andshift registers to control burst generators.

FIG. 66 shows a flow diagram for controlling trigger generator 2200shown in FIG. 65.

FIG. 67 shows one embodiment of a parallel-to-serial shift register.

FIG. 68 shows an alternative embodiment of a trigger generator using anencoder and a time slot counter to control burst generators.

FIG. 69 shows a flow diagram for controlling trigger generator 2300shown in FIG. 68.

FIG. 70 shows an embodiment of a signal decoder using detector captureregisters, serial-to-parallel shift registers and a decoder.

FIG. 71 shows a flow diagram for controlling signal decoders 1100 and1400 shown in FIG. 70 and FIG. 73, respectively.

FIG. 72 shows an embodiment of a serial-to-parallel shift register.

FIG. 73 shows an alternative embodiment of a signal decoder.

DETAILED DESCRIPTION

In the description and claims that follow, certain terms may be definedas follows:

The term ‘frequency band’ denotes a portion of the frequency spectrum.The term ‘center frequency’ as applied to a frequency band denotes afrequency at the arithmetic mean of the frequencies of the boundaries ofthe frequency band. As defined herein, frequency bands may be adjacentto one another but are distinct from one another and do not overlap.

The term ‘burst’ denotes the emission of an amount of energy within aparticular range of frequencies and over a limited period of time. Aburst may include one or more cycles of a waveform (e.g. a sine wave). Aburst may even be limited to less than one cycle of a waveform. In someapplications, two or more bursts may be transmitted simultaneously.Beginning the transmission of a burst is also referred to as‘triggering’ the burst. Transferring a burst from the generatingcircuitry (e.g. as described herein) to the transmission medium orchannel is also referred to as ‘launching’ the burst.

The term ‘bandwidth’ denotes a continuous range of frequencies thatcontains at least 90% and not more than 95% of the total energy of asignal. The bandwidth of a burst may lie within more than one frequencyband at a time. The term ‘center frequency’ as applied to a burstdenotes the midpoint (along the frequency axis) of the energydistribution of the burst: i.e. the frequency at which the total energyof the burst on either side is fifty percent of the total energy of theburst (as in the examples illustrated in FIG. 59). A burst ‘occupies’ afrequency band when the center frequency of the burst is within thefrequency band, such that a burst occupies no more than one frequencyband at a time.

The term ‘wideband’ denotes a signal whose bandwidth is not less than 2%of its center frequency, and the term ‘ultra-wideband’ denotes a signalwhose bandwidth is not less than 20% of its center frequency. Forexample, the bandwidth of an ultra-wideband signal may be up to 50% ormore of the signal's center frequency. Ultra-wideband signals may beused at frequencies from less than tens of hertz to terahertz andbeyond. Although most ultra-wideband use currently falls between 100 MHzand 10 GHz primarily due to present-day regulatory allocations, it isenvisioned that future allocations will extend far beyond this frequencyrange.

FIG. 1 shows an example in the time domain of bursts in three differentfrequency bands (illustrated as waveforms 1, 2 and 3). FIG. 2 shows analternative representation of these three bursts in the frequencydomain, where frequency bands 4, 5, and 6 correspond to waveforms 1, 2,and 3, respectively. In this example, the three frequency bands areeasily distinguished from one another in the frequency domain.

The term ‘time slot’ denotes a defined period of time that separatesmoments at which bursts may be triggered. It may be desirable to observea convention of triggering bursts only at the start of a time slot, suchthat during each time slot, no more than one burst is triggered perfrequency band.

A period of time may be divided into a continuous series of consecutiveand non-overlapping time slots of equal duration. Alternatively, sets ofconsecutive and non-overlapping time slots of one duration may beseparated in time by one or more time slots of a different (e.g. alonger or even a shorter) duration. In a complex high-speed system, thelength of a time slot may be measured in picoseconds. In a lower-speedsystem of less complexity, the length of a time slot may be in thenanosecond range. In other applications, time slots of shorter orgreater length may be used as desired.

In the implementations described herein, the same time slot boundariesare observed across the various frequency bands. However, it iscontemplated that two or more different time slot arrangements may beapplied among the various frequency bands (e.g. that time slots in onefrequency band may be longer than time slots in another frequency band,or that time slots in one frequency band may have constant length whiletime slots in another frequency band have varying length) in otherimplementations.

FIG. 3 is an illustration of two examples in which sets of time slotsare separated by periods during which no bursts are launched (‘quiettime’). In example 3A (where different shadings indicate differentfrequency bands), each burst 12, 13 and 14 has a duration shorter thanthat of a time slot. However, it is also contemplated that in someapplications a burst may have a duration longer than a time slot (e.g.as in example 3B), such that two or more bursts 25, 26, 27, 28, 29 mayoverlap even if their corresponding time slots do not (e.g., bursts 25and 26 overlap in time). In such cases, a series of bursts triggeredduring consecutive time slots in the same frequency band may representdifferent information than a single burst that extends over the samenumber of time slots.

The term ‘symbol’ denotes an ordered series of n-tuples that correspondsto an ordered set of data values. The term ‘cluster’ (e.g., clusters10A, 16, 22, 24) denotes a set of bursts corresponding to a symbol. Theterm ‘symbol interval’ denotes the period between the start oftransmission of a cluster and the start of transmission of the nextcluster and includes any ‘quiet time’ (e.g., quiet time 15, 23) betweenthe clusters. These terms are also illustrated by example in FIG. 3 andin FIG. 4, which shows consecutive clusters that each includeoverlapping bursts. In some applications as described herein, it ispossible for no bursts to be launched during one or more of the timeslots in each cluster.

‘Quiet time’ periods between clusters may be especially useful, forexample, in asynchronous applications. In such cases, it may bedesirable for the duration of a quiet time period to be greater than theduration of a time slot.

In some applications, clusters may not overlap (e.g., to reduceinterference). FIG. 5 shows one example of a cluster that includes threebursts 50, 51, 52 triggered at consecutive time slots. In this example,the start of each burst is delayed by about 2.5 nanoseconds from thestart of the previous burst.

FIG. 6 shows the cluster of FIG. 5 in the frequency domain. Although thethree bursts 50, 51, 52 overlap in frequency, they may still bedistinguished at, e.g., their center frequencies. FIG. 7 shows atime-domain plot of a cluster that includes bursts which overlap intime. In some applications, bursts that overlap in time may be used(e.g. to support higher rates of data transfer) and/or bursts thatoverlap in frequency may be used (e.g. to support higher data density).

According to several embodiments of the invention, and as used herein,“time division multiple frequency” or TDMF is generally an encodingscheme that encodes information (bits) in the time order of transmissionof at least one burst within each of multiple sub-bands. That is, datais encoded through the time dependence of frequency bursts within acluster of bursts. The time and the frequency band at which bursts occurwithin a cluster carry the information. For example, the order oftransmission of bursts across the multiple sub-bands defines a symbol,the symbol corresponds or maps to defined bits. For example, asillustrated in FIG. 5, a cluster consisting of a time-sequence of threebursts 50, 51 and 52 transmitted in successive time slots encodes asymbol, which corresponds to a specific set of data. In preferredembodiments, each burst has a bandwidth of at least 2% of its centerfrequency, and more preferably at least 20% of its center frequency.

FIG. 8 shows a flowchart of a method according to an embodiment of theinvention. Task T100 encodes an ordered set (e.g. ordered in time and/orplace) of m data values (e.g. data bits) into a symbol that includes aseries of p ordered n-tuples (where m and p are integers greater thanzero, and n is an integer greater than one). Task T200 transmits thesymbol as a cluster that includes a time sequence of bursts across nfrequency bands and over p time slots. For example, task T200 maytransmit the symbol such that the i-th element of each n-tuplecorresponds to the i-th frequency band, and the j-th n-tuple correspondsto the j-th time slot. According to the particular application, overlapin time of bursts on different frequency bands may or may not bepermitted in task T200.

In an operation of data transfer according to an implementation of thismethod, the (i,j)-th element of the series of n-tuples indicatesactivity on the i-th frequency band during the j-th time slot. In a baseimplementation, each element is binary-valued, such that its valueindicates either a presence (e.g. ‘1’ or ‘high’) or an absence (e.g. ‘0’or ‘low’) of a burst. In this base implementation, it is also assumedthat a length of each burst is arbitrarily less than one time slot, thata polarity of each burst is constant or arbitrary, and that (e.g. forfree space and optical applications) a polarization of the transmittedbursts is arbitrary. As discussed below, in other implementationsadditional information may be supplied (e.g. encoded within the seriesof n-tuples, or provided in addition to such series) to indicate suchqualities of a burst or cluster as amplitude, width, polarity, and/orpolarization.

Task T100 may be performed by mapping the ordered set of m data valuesinto one of the possible symbol states for the selected encoding scheme.FIG. 9 illustrates such an encoding for one scheme in which each symbolhas four n-tuples. In this particular example, the n-tuples areconstrained such that two and only two elements of each n-tuple arehigh-valued, with the other values of the n-tuple being low-valued. Sucha restriction may be observed in practice, for example, to maintain aconstant or relatively constant level of energy during transmission of astream of clusters across the transmission channel.

In such a scheme, each n-tuple has (four choose two) or six possiblestates, as set forth in the table in FIG. 9. The number of possiblestates for each symbol in this case is equal to the number of states pern-tuple, raised to the power of the number of time slots (here, 6⁴ or1296 possible states).

FIG. 9 includes a flowchart that demonstrates an example of encoding a10-bit binary number into a series of four ordered 4-tuples according tothis scheme. By way of explanation, FIG. 9 shows this task as a two-stepprocedure. First, the input string is converted from a ten-digit numberin base two to a four-digit number in base six. Second, each of the fourdigits of the base-six intermediate result is mapped to a correspondingn-tuple state as shown in the table, yielding the encoded symbol as aseries of 4 ordered 4-tuples (the mapping shown in the table is only oneof many possible different mappings). While in this example each n-tuplehas a one-to-one correspondence with a digit of the base-sixintermediate result, at least some of the elements of the n-tuples havea one-to-many correspondence with the values of the binary input string.Therefore, an n-tuple may represent information that relates to morethan one of the input data values.

Note that the two-step procedure of FIG. 9 is shown by way of exampleonly. In practice, task T100 may map the input set directly to acorresponding output series using, e.g., a lookup table or equivalentarrangement of combinatorial logic elements.

FIG. 10 shows a pictorial representation of the distribution of thesymbol of FIG. 9 over corresponding frequency bands and time slotsaccording to one possible distribution scheme. Note that this particularsymbol indicates activity in frequency band one during all four timeslots. Depending upon the application, this indication will correspondunambiguously to one burst that is active in four consecutive timeslots, or to two bursts that are each active in two consecutive timeslots (or respectively in one and three consecutive time slots), or tofour bursts that are each active in one time slot. As noted above, weassume in this example that the indication corresponds to four separatebursts. FIG. 11 shows a similar representation of a sequence of clustersover time.

More specifically, FIG. 11 illustrates a sequence of multi-band clustersof bursts, e.g., clusters 90, 92, 94 and 96 each composed of multiplebursts in different frequency bands with a cluster interval between thestart of successive clusters. In this example, there are five availablefrequency bands, f₁, f₂, f₃, f₄ and f₅. Bursts (indicated in shaded timeslots) are transmitted in one of five time slots in one of fivefrequency bands. In one embodiment, the time dependence of bursts acrossfrequency for each cluster encodes a symbol, the symbol mapping tospecific data. In cluster 92, it can be seen that multiple bursts may betransmitted at the same time (i.e., three bursts are transmitted in thefirst time slot), while in cluster 94, only one burst is sent duringeach time slot. As described in more detail further below, this schememay be varied in numerous ways. For example, the polarity, amplitude,width and/or polarization of each burst of a given cluster may bemodulated to encode additional bits into the cluster.

In some schemes, the input set may have fewer possible states than theoutput symbol. In the scheme illustrated in FIG. 9, for example, eachinput set of 10 bits may have 2¹⁰ or 1024 different states, while eachcorresponding output symbol may have 6⁴ or 1296 different states. Whilethe additional output states (272 states per symbol in this case) may beignored in some applications, in other applications they may be used tocarry information. For example, these states may be used to transferinformation such as one or more additional data streams, possibly at adifferent data transfer rate.

In one example as applied to the scheme of FIG. 9, 256 of the 272additional states are used to carry a different input stream of 8-bitwords (each word having 2⁸ or 256 possible states), while the remaining16 additional states could even be used to carry a third input stream of4-bit words (each word having 2⁴ or 16 possible states). Alternatively,symbols not used for data can be used to convey control information fromtransmitter to receiver. For example, one or more otherwise unusedsymbol states can be used for synchronization or other timing purposes,to control a decoder initial state, to indicate a change in modulationscheme, etc. In some cases, one or more unmapped symbol states may beused to maintain signal activity or homogeneity (i.e. for transmissionduring a period when no input data is available for transfer).

In some applications, symbol states that are not mapped to input setsmay be used for signal source identification. For example, one or moreunused symbol states may be assigned to a transmitter for use as anidentifier. A signal that includes this symbol or symbols may then bedistinguished from the signals of other transmitters in the vicinity(e.g. minimizing false alarms due to interference from othertransmitters or emitters). Transmitter identification may be used tosupport networking and transmitter location and position determinationapplications as disclosed herein.

In other applications, a label that distinguishes one transmitter fromanother may itself serve as the ordered set of m data values that isencoded to produce the symbol. In one such application, a transmitter isconfigured to transmit (e.g. at some predetermined interval) one or moreclusters corresponding to its label. The location of the transmitter isthen determined by comparing the arrival times of the cluster(s) atseveral (preferably three or more) receivers. An example system uses oneor more low-cost, low-power versions of such a transmitter as ‘smarttags’, e.g. for tracking the locations of boxes in a warehouse.Additional location and position determination techniques andapplications are discussed below.

In a basic modulation scheme according to an embodiment of the invention(hereinafter ‘scheme A’), each time slot may have any number of burstsfrom zero to n. Therefore, each symbol may have 2^(np) different states.Such a scheme may be applied to synchronous or asynchronous operations,and the transmission channel may be wired, wireless, or optical (whetherthrough free space or through fiber or another medium).

By varying such system parameters as the number of burstspermitted/required per time slot, the number of time slots per cluster,the number of frequency bands, whether the first time slot of a clusteris required to be occupied by at least one burst, and whether a clustermust include at least one burst in each frequency band, many differentschemes may be designed to suit many different situations. For example,a scheme that maximizes data transfer rate may be adopted for anoise-free application, while a scheme that maximizes symbol trackingperformance may be adopted for an asynchronous application, while ascheme that balances data transfer rate and error detection capabilitymay be adopted for another application. Various example schemes asapplied to the base implementation are described below.

In one such scheme, at least one burst occurs during each time slot,such that no time slot within a symbol is empty. Such a scheme mayprovide a benefit in asynchronous operations (e.g. easier tracking). Inthis example, each symbol may have (2^(n)−1)^(p) different states.

In another scheme, one and only one burst occurs during each time slot.Such a scheme may support asynchronous operations and/or offer reducedpower output, for example, at the cost of reduced rate of data transfer.Each symbol according to this example may have n^(p) different states.

In another scheme, up to n bursts occur during each time slot, andexactly one burst occurs per frequency band per cluster (in this scheme,the number of time slots p is not less than the number of frequencybands n). The constraint of one burst per frequency band per cluster mayprovide better performance in environments prone to reflection ormultipath interference. Such a scheme may also be expected to providebetter error detection capability at the expense of a reduced datatransfer rate. Each symbol according to this example may have p^(n)different states (e.g. 100,000 different states for n=5 and p=10, or3125 different states for n=p=5).

In another scheme, one and only one burst occurs during each time slot,and no more than one burst occurs per frequency band per cluster (inthis scheme, the number of time slots p is not less than the number offrequency bands n). Each symbol in this example may have n!/(n−p)!different states.

In one variation of the scheme above (one and only one burst per timeslot, and no more than one burst per frequency band per symbol), thefirst time slot of a cluster is unavailable for data transfer. Forexample, such a variation may be used to implement a logicalchannelization scheme in which the active frequency in the first timeslot identifies the particular logical channel over which the cluster isbeing transmitted. (Division of a physical channel into more than onelogical channel, and other techniques for such division, are discussedin more detail below.) Each symbol in this example may have up to(n−1)!/(n−p)! different data states.

In another scheme, no more than one burst occurs during each time slot,and exactly one burst occurs per frequency band per cluster (in thisscheme, the number of time slots p is not less than the number offrequency bands n). This example scheme also includes the feature thatthe first time slot of each cluster is not empty; this feature (whichmay be especially useful in asynchronous applications) could be appliedto provide a relative time reference at the receiver. In this case, eachsymbol may have up to n(p−1)!/(p−n)! different states (e.g. 15,120different states for n=5 and p=10, or 120 different states for n=p=5).

In another scheme, no more than one burst occurs during each time slot,no more than one burst occurs per frequency band per cluster, and thefirst time slot of each cluster is not empty (in this scheme, the numberof time slots p is not less than the number of frequency bands n). Inthis case, the number of different states available for each symbol maybe expressed as the sum over k (1≦k≦n) of the number of clusters havingbursts on exactly k frequency bands, or

$\sum\limits_{k = 1}^{n}\;{\begin{pmatrix}n \\k\end{pmatrix}k\frac{\left( {p - 1} \right)!}{\left( {p - k} \right)!}}$(e.g. 27,545 different states for n=5 and p=10, or 1045 different statesfor n=p=5).

In another scheme, up to n bursts may occur during each time slot,exactly one burst occurs per frequency band per cluster, and the firsttime slot of each cluster is not empty (in this scheme, the number oftime slots p is not less than the number of frequency bands n). In thiscase, the number of different states available for each symbol may beexpressed as

$\sum\limits_{k = 1}^{n}\;{\begin{pmatrix}n \\k\end{pmatrix}\left( {p - 1} \right)^{n - k}}$(e.g. 40,951 different states for n=5 and p=10, or 2101 different statesfor n=p=5).

In another scheme, up to n bursts may occur during each time slot, nomore than one burst occurs per frequency band per cluster, and the firsttime slot of each cluster is not empty (in this scheme, the number oftime slots p is not less than the number of frequency bands n). In thiscase, the number of different states available for each symbol may beexpressed as

$\sum\limits_{k = 1}^{n}\;{\begin{pmatrix}n \\k\end{pmatrix}{\sum\limits_{m = 1}^{k}\;{\begin{pmatrix}k \\m\end{pmatrix}\left( {p - 1} \right)^{k - m}}}}$(e.g. 61,051 different states for n=5 and p =10, or 4651 differentstates for n=p=5).

In another scheme, up to n bursts may occur during each time slot, nomore than one burst occurs per frequency band per cluster, and eachcluster includes at least one burst (i.e. no cluster is empty) (in thisscheme, the number of time slots p is not less than the number offrequency bands n). In this case, the number of different statesavailable for each symbol may be expressed as

$\sum\limits_{k = 1}^{n}\;{\begin{pmatrix}n \\k\end{pmatrix}p^{k}}$(e.g. 161,050 different states for n=5 and p=10, or 7775 differentstates for n=p=5).

In another scheme, up to r (r≦n) bursts occur during each time slot,exactly one burst occurs per frequency band per cluster, and the firsttime slot of each cluster is not empty (in this scheme, the number oftime slots p is not less than the number of frequency bands n). In thiscase, the number of different states available for each symbol may beexpressed as nc(r,n,p) using the following recursive formula:

nc(r, nf, 1) = 1${{{nc}\left( {r,{nf},{n\; s}} \right)} = {\sum\limits_{\substack{s = {s\; 1} \\ {M{({{n\; s} - 1})}} \geq {{nf} - s}}}^{\min{({r,{nf}})}}\;{\begin{pmatrix}{nf} \\s\end{pmatrix}{{nc}\left( {M,{{nf} - s},{{n\; s} - 1}} \right)}}}},$

where the parameter nf denotes the number of frequency bands stillunassigned in the cluster; the parameter ns denotes the number of timeslots remaining in the cluster; the constraint M(ns−1)≧(nf−s) requiresthat the product of the number of time slots that will remain and themaximum number of bursts per time slot is sufficiently large to permitassignment of the frequency bands that will remain; nc(A,B,C) denotesthe number of combinations for up to A bursts per time slot, B frequencybands still unassigned in the cluster, and C time slots remaining in thecluster; and the parameter s1 has the value

${s\; 1} = \left\{ {\begin{matrix}{0,} & {{n\; s} < p} \\{1,} & {{n\; s} = p}\end{matrix}.} \right.$For such a scheme in which each symbol has five n-tuples, the number ofdifferent states available for each symbol is indicated in the followingtable as a function of n and r:

r = 1 r = 2 r = 3 r = 4 r = 5 n = 1 1 — — — — n = 2 8 9 — — — n = 3 3660 61 — — n = 4 96 336 368 369 — n = 5 120 1620 2060 2100 2101

In another scheme, exactly one burst occurs per frequency band percluster, the first time slot of each cluster is not empty, and from oneto r bursts occur during each time slot until no unassigned frequencybands remain (in this scheme, the number of time slots p is not lessthan the number of frequency bands n). In this case, the number ofdifferent states available for each symbol may be expressed as nc(r,n,p) using the recursive formula above, except that s1=1 for anyvalue of ns.

Again, it is noted that the number of states per symbol indicated forthe above examples assumes without limitation that each element of eachn-tuple is binary-valued. Variations of such schemes in which one ormore elements of an n-tuple may have additional values are specificallycontemplated and enabled herein.

Many other schemes may be implemented according to such principles. Forexample, in addition to variations to the base implementation asmentioned above, characteristics of such schemes may include a minimumnumber of time slots between bursts on the same frequency band (whichminimum number may be different for different frequency bands), amaximum and/or minimum number of bursts during one time slot, a minimumnumber of time slots per burst, a maximum and/or minimum number ofconsecutive empty time slots, etc. Depending on its nature, a particularvariation or characteristic may be applied during encoding of the dataset and/or during transmission of the symbol.

As noted above, the duration of an individual burst may be longer orshorter than the corresponding time slot. For timing purposes, it may bedesirable to synchronize the start of a burst with the start of thecorresponding time slot. However, other timing schemes are possible.

Bursts having one time relation that are transmitted over differentfrequency bands may propagate through a dispersive communicationschannel such that the bursts have a different time relation uponreception. For example, bursts at different frequency bands may bereflected differently in the environment, within the transmitter, withinthe receiver, etc. In some applications, the timing of bursttransmissions among the various n frequency bands may be modified toadjust for expected propagation delays. For example, burst transmissionsmay be timed such that bursts within the same time slot may be expectedto arrive at the receiver at substantially the same time. Suchmodification may be based on a prior determination (e.g. calculationand/or measurement) and/or may be performed adaptively during operationthrough a mechanism such as dynamic calibration. FIG. 12 shows a diagramof one such application in which bursts in higher frequency bands aretransmitted earlier than bursts in lower frequency bands, according toan expected (e.g. calculated, calibrated, and/or observed) difference inpropagation delay.

In another example, the addition of a random (or pseudorandom) timeperturbation may reduce peak power levels on a nominally periodic trainof symbols. FIG. 13 shows an effect of application of random delayperturbations (or ‘jitter’) to a simulated transmission of 100 clustersusing frequency bands centered at 3.5 and 4 GHz, repeated 20 times, withtwo bursts per cluster, burst duration 5 ns, quiet time period 40 ns,and symbol interval 50 ns. The bottom plot shows the spectrum thatoccurs when the same train of clusters is sent using a random delay of±10 ns.

In other implementations of a method according to several embodiments ofthe invention, one or more additional modulations may be added to thetechniques described thus far to encode additional information (e.g.,bits) into the transmitted bursts and/or clusters. For example, whileone or more elements of a given n-tuple indicates which frequency bandand timeslot to transmit a given burst within a cluster, one or moreelements of the n-tuple indicate a modulation variation to be applied toa particular burst(s) and/or cluster. The number of possible symbolstates in a particular modulation scheme (e.g. as configured at aparticular time) may be a function of several parameters such as thenumber of frequency bands n and the number of time slots p. For example,the data transfer rate of a system may be effectively limited by thenumber of frequency bands n (with other parameters being fixed). In somecases, it may be desirable to add an additional or supplementalmodulation to a modulation scheme as described or suggested herein toincrease the number of data values that may be transferred during adesignated time period. Examples of such additional or supplementalmodulations include polarity, amplitude, width and polarizationmodulations.

According to one example, an element of the n-tuple (e.g., out of aseries of n-tuples defining a symbol) indicates that a burst is to betransmitted during a given timeslot and in a given frequency band, whileanother element of the n-tuple indicates the polarity of the burst to betransmitted. The additional modulation (i.e., polarity modulation inthis case) adds additional information to the transmitted clusterwithout transmitting additional bursts. Thus, advantageously, theadditional modulation makes possible to encode additional bits ofinformation into the transmitted signal (cluster), which can increasethe data transfer rate of information within the same time period.Following are more detailed descriptions of additional modulations thatmay be applied or encoded into the transmitted signaling. It isunderstood that other additional modulations not specifically describedmay be added without departure from these embodiments of the invention.

In other implementations of a method according to an embodiment of theinvention, polarity modulation is used to additionally modulate thesignal, e.g., a value of at least one element of a series of n-tuplesindicates a polarity of the corresponding burst. FIG. 13A shows oneexample of a cluster that includes bursts that are polarity modulated.In this example, the first burst 53 of the cluster is centered at afirst frequency, the second burst 54 is also centered at the firstfrequency but has a polarity opposite to that of the first burst, andthe third burst 55 is centered at a second (higher) frequency. The thirdburst may have information encoded in its polarity or may have a presetor arbitrary polarity.

Polarity modulation may be applied in many different ways. For example,polarity modulation may be applied burst-wise. In an entirely burst-wisescheme, the polarity of each burst of a cluster is independentlymodulated, although some bursts may remain unmodulated. FIG. 13A showsan example of a cluster that is burst-wise polarity modulated.

Alternatively, polarity modulation may be applied other than burst-wisesuch that the polarity of one burst depends upon (or has a predeterminedrelation to) the polarity of at least one other burst. In one suchscheme, all of the bursts of a cluster have the same polarity. It isalso possible to implement a polarity modulation scheme that is bothburst-wise with respect to some bursts and dependent with respect toother bursts. Two or more bursts having a dependent polarity relationneed not be in adjacent frequency bands or time slots. Also, two or morebursts having a dependent polarity relation need not have the samepolarity (e.g. a pair of bursts may be modulated to have oppositepolarities).

FIG. 13B shows an example of two clusters having identical frequencycontent that are polarity modulated using a cluster-wise scheme. Thefirst cluster includes three bursts (bursts 56, 57, 58) of differentfrequencies, each having a defined first polarity. The second clusterincludes three bursts (bursts 59, 60, 61), each having the samefrequency as the corresponding one of the first cluster but the oppositepolarity. In a cluster-wise scheme, the polarity of each cluster may beindependently modulated, or some clusters may remain unmodulated.Polarity modulation may also be applied other than cluster-wise suchthat the polarity of one cluster depends upon (or has a predeterminedrelation to) the polarity of at least one other cluster.

The number of possible symbol states in a particular modulation scheme(e.g. as configured at a particular time) may be a function of severalparameters such as the number of frequency bands n and the number oftime slots p. For example, the data transfer rate of a system may beeffectively limited by the number of frequency bands n (with otherparameters being fixed). In some cases, it may be desirable to addpolarity modulation to a modulation scheme as described or suggestedherein to increase the number of data values that may be transferredduring a designated time period.

In scheme A as described above, each time slot may have any number ofbursts from zero to n, and accordingly each symbol may have 2^(np)different possible states. Burst-wise polarity modulation may be addedto this basic scheme to obtain a variation in which each symbol may have3^(np) different possible states.

For a different modulation scheme in which a cluster includes exactly nfrequency bursts over p time slots (hereinafter ‘scheme B’), each symbolmay have n^(p) possible states. By adding burst-wise polarity modulationto such a scheme, the capability of the system may be increased to(2n)^(p) possible states per symbol. If scheme B is applied to aparticular example in which n=p=3, each symbol has 3³=27 possible statesbefore polarity modulation and can encode four full bits of digitaldata, and after burst-wise polarity modulation each symbol has(2×3)³=6³=216 possible states and can encode seven full bits of digitaldata.

Applying cluster-wise polarity modulation to scheme B increases thecapability of each symbol to 2(n^(p)) possible states. If scheme B isapplied to a particular example in which n=p=3, each symbol has 3³=27possible states before polarity modulation and can encode four full bitsof digital data, and after cluster-wise polarity modulation each symbolhas 2×(3)³=54 possible states and can encode five full bits of digitaldata.

As mentioned above, a scheme having a constraint of one burst perfrequency band per cluster may provide better performance in anenvironment prone to reflection or multipath interference (such asterrestrial free space) than a scheme that does not observe such aconstraint. A scheme having this constraint may also be expected toprovide better error detection capability at the expense of a reduceddata transfer rate.

In one variation of such a scheme, a further constraint of one and onlyone burst per time slot is also applied, with the number of time slots pbeing not less than the number of frequency bands n (hereinafter ‘schemeC’). Each symbol in this scheme may have p!/(p−n)! different states.

For the particular case of scheme C in which n=p, each symbol may haven! possible states. By applying burst-wise polarity modulation to thisinstance of scheme C, an implementation having n!2′ possible states persymbol may be obtained. For n=p=3, each symbol under scheme C may havesix possible states and can encode two full bits of digital data. Byapplying burst-wise polarity modulation, the capacity of each symbolincreases to 48 states, such that each symbol can encode five full bitsof digital data.

By applying cluster-wise polarity modulation to the (n=p) instance ofscheme C, an implementation having n!2 possible states per symbol may beobtained. For n=3, each symbol under this instance of scheme C may havesix possible states and can encode two full bits of digital data. Byapplying cluster-wise polarity modulation, the capacity of each symbolincreases to 12 states, such that each symbol can encode three full bitsof digital data.

The examples of polarity modulation described above assume that a burstmay have three states with respect to a particular time slot: absent,present with a first polarity, or present with a second polarityopposite to the first polarity. In some implementations, it may bedesirable to restrict the allowed states of some or all bursts. Forexample, it may be desirable for a burst to be always present withrespect to a particular time slot, such that the burst is allowed tohave only the two polarity states. In another example, it may bedesirable to restrict some bursts to have only the absent and firstpolarity states, while other bursts are restricted to have only theabsent and second polarity states. Such implementations may be desirablefor purposes such as synchronization, channel power uniformity, and/orcoding design.

In a system employing polarity modulation, it may be desirable for atransmitter to transmit one or more bursts of predetermined polarity toprovide a polarity reference. For example, the polarity of a burstwithin a cluster may be assigned with respect to the first burst of thecluster. Dynamic comparison of a received burst or cluster to one ormore previously received bursts or clusters may also be used todetermine a polarity state that has been distorted during propagationthrough the transmission channel. Alternatively, polarity modulation maybe applied using a channel coding scheme (such as Walsh coding) toresolve ambiguity in the polarity of the received bursts without theneed for a polarity reference.

In other implementations of a method according to an embodiment of theinvention, amplitude modulation is used to additionally modulate thesignal, e.g., at least one element of the series of n-tuples has one ofq distinct values, such that its value indicates an amplitude of thecorresponding burst. Such amplitude modulation may be added to a schemeas described or suggested above to increase the number of data valuesthat may be transferred during a designated time period. Addingburst-wise amplitude modulation to scheme A, for example, may result ina system in which each symbol has q^(np) different possible states.

FIG. 13C shows one example of a cluster that includes bursts that areamplitude modulated. In this example, the first burst 62 of the clusteris centered at a first frequency, the second burst 63 is also centeredat the first frequency but has an amplitude that is one-half theamplitude of the first burst, and the third burst 64 is centered at asecond (higher) frequency and has the same amplitude as the first burst.The third burst may have information encoded in its amplitude or mayhave a preset or arbitrary amplitude.

Amplitude modulation may be applied in many different ways. For example,amplitude modulation may be applied burst-wise. In an entirelyburst-wise scheme, the amplitude of each burst of a cluster isindependently modulated, although some bursts may remain unmodulated.FIG. 13C shows an example of a cluster that is burst-wise amplitudemodulated.

Alternatively, amplitude modulation may be applied other than burst-wisesuch that the amplitude of one burst depends upon (or has apredetermined relation to) the amplitude of at least one other burst. Inone such scheme, all of the bursts of a cluster have the same amplitude.It is also possible to implement an amplitude modulation scheme that isboth burst-wise with respect to some bursts and dependent with respectto other bursts. Two or more bursts having a dependent amplituderelation need not be in adjacent frequency bands or time slots. Also,two or more bursts having a dependent amplitude relation need not havethe same amplitude (e.g. a pair of bursts may be modulated to haverelated but different amplitudes).

FIG. 13D shows an example of two clusters having identical frequencycontent that are amplitude modulated using a cluster-wise scheme. Thefirst cluster includes three bursts (bursts 65, 66, 67) of differentfrequencies, each having a defined first amplitude. The second clusterincludes three bursts (bursts 68, 69, 70), each having the samefrequency as the corresponding one of the first cluster but a secondamplitude lower than the first amplitude. In a cluster-wise scheme, theamplitude of each cluster may be independently modulated, or someclusters may remain unmodulated. Amplitude modulation may also beapplied other than cluster-wise such that the amplitude of one clusterdepends upon (or has a predetermined relation to) the amplitude of atleast one other cluster.

In scheme B as described herein, each symbol may have n^(p) possiblestates. By adding burst-wise amplitude modulation to such a scheme, thecapability of the system may be dramatically increased to (nq)^(p)possible states, where q is the number of distinct amplitude levelsemployed. If scheme B is applied to a particular example in which n=p=3,each symbol has 3³=27 possible states before amplitude modulation andcan encode four full bits of digital data, and after two-levelburst-wise amplitude modulation each symbol has (2×3)³=6³=216 possiblestates and can encode seven full bits of digital data. A higher numberof distinct amplitude levels may be used to further increase the numberof possible states per symbol.

Applying cluster-wise amplitude modulation to scheme B increases thecapability of each symbol to q(n^(p)) possible states. If scheme B isapplied to a particular example in which n=p=3, each symbol has 3³=27possible states before amplitude modulation and can encode four fullbits of digital data, and after two-level cluster-wise amplitudemodulation each symbol has 2×(3)³=54 possible states and can encode fivefull bits of digital data. A higher number of distinct amplitude levelsmay be used to further increase the number of possible states persymbol.

In scheme C as described above, each symbol may have p!/(p−n)! differentstates, and if n equals p, then the possible states per symbol is n!. Byapplying burst-wise amplitude modulation to this particular instance ofscheme C, an implementation having n! q^(n) possible states per symbolmay be obtained. For n=p=3, each symbol under this scheme may have sixpossible states and can encode two full bits of digital data. Byapplying two-level burst-wise amplitude modulation, the capacity of eachsymbol increases to 48 states, such that each symbol can encode fivefull bits of digital data.

By applying cluster-wise amplitude modulation to the (n=p) instance ofscheme C, an implementation having n!q possible states per symbol may beobtained. For n=3, each symbol under this instance of scheme C may havesix possible states and can encode two full bits of digital data. Byapplying two-level cluster-wise amplitude modulation, the capacity ofeach symbol increases to 12 states, such that each symbol can encodethree full bits of digital data.

In a system employing amplitude modulation, it may be desirable for atransmitter to transmit one or more bursts of predetermined amplitude toprovide an amplitude reference. For example, the amplitude of a burstwithin a cluster may be assigned with respect to the amplitude of thefirst burst of the cluster. Alternatively, one burst within a sequenceof clusters may serve as a reference for the other bursts in thesequence.

In other implementations of a method according to an embodiment of theinvention, polarization modulation is used to additionally modulate thesignal, e.g., a value of at least one element of a series of n-tuplesindicates a polarization of the corresponding burst (e.g. vertical,horizontal, left-hand circular, right-hand circular, etc.). FIG. 13Eshows one example of a cluster that includes bursts that arepolarization modulated. In this example, the first burst 71 of thecluster is centered at a first frequency, the second burst 72 is alsocentered at the first frequency but has a polarization different fromthat of the first burst, and the third burst 73 is centered at a second(higher) frequency. The third burst may have information encoded in itspolarization or may have a preset or arbitrary polarization.

Polarization modulation may be applied in many different ways. Forexample, polarization modulation may be applied burst-wise. In anentirely burst-wise scheme, the polarization of each burst of a clusteris independently modulated, although some bursts may remain unmodulated.FIG. 13E shows an example of a cluster that is burst-wise polarizationmodulated.

Alternatively, polarization modulation may be applied other thanburst-wise such that the polarization of one burst depends upon (or hasa predetermined relation to) the polarization of at least one otherburst. In one such scheme, all of the bursts of a cluster have the samepolarization. It is also possible to implement a polarization modulationscheme that is both burst-wise with respect to some bursts and dependentwith respect to other bursts. Two or more bursts having a dependentpolarization relation need not be in adjacent frequency bands or timeslots. Also, two or more bursts having a dependent polarization relationneed not have the same polarization (e.g. a pair of bursts may bemodulated to have orthogonal polarizations).

FIG. 13F shows an example of two clusters having identical frequencycontent that are polarization modulated using a cluster-wise scheme. Thefirst cluster includes three bursts (bursts 74, 75, 76) of differentfrequencies, each having a defined first polarization. The secondcluster includes three bursts (bursts 77, 78, 79), each having the samefrequency as the corresponding one of the first cluster but a differentpolarization. In a cluster-wise scheme, the polarization of each clustermay be independently modulated, or some clusters may remain unmodulated.Polarization modulation may also be applied other than cluster-wise suchthat the polarization of one cluster depends upon (or has apredetermined relation to) the polarization of at least one othercluster.

In some cases, it may be desirable to add polarization modulation to amodulation scheme as described or suggested herein to increase thenumber of data values that may be transferred during a designated timeperiod. In scheme A as described above, each time slot may have anynumber of bursts from zero to n, and accordingly each symbol may have2^(np) different possible states. Burst-wise polarization modulation maybe added to this basic scheme to obtain a variation in which each symbolmay have v^(np) different possible states, where v denotes the number ofdifferent polarization states being implemented.

In scheme B as described above, each symbol may have n^(p) possiblestates. By adding burst-wise polarization modulation to such a scheme,the capability of the system may be increased to (vn)^(p) possiblestates per symbol. If scheme B is applied to a particular example inwhich n=p=3, each symbol has 3³=27 possible states before polarizationmodulation and can encode four full bits of digital data, and aftertwo-state burst-wise polarization modulation (e.g. vertical/horizontal,or left-hand/right-hand circular) each symbol has (2×3)³=6³=216 possiblestates and can encode seven full bits of digital data.

Applying cluster-wise polarization modulation to scheme B increases thecapability of each symbol to v(n^(p)) possible states. If scheme B isapplied to a particular example in which n=p=3, each symbol has 3³=27possible states before polarization modulation and can encode four fullbits of digital data, and after two-state cluster-wise polarizationmodulation each symbol has 2×(3)³=54 possible states and can encode fivefull bits of digital data.

In scheme C as described herein, each symbol may have p!/(p−n)!different states. For the particular case of scheme C in which n=p, eachsymbol may have n! possible states. By applying burst-wise polarizationmodulation to this instance of scheme C, an implementation havingn!v^(n) possible states per symbol may be obtained. For n=p=3, eachsymbol under scheme C may have six possible states and can encode twofull bits of digital data. By applying two-state burst-wise polarizationmodulation, the capacity of each symbol increases to 48 states, suchthat each symbol can encode five full bits of digital data.

By applying cluster-wise polarization modulation to the (n=p) instanceof scheme C, an implementation having n!v possible states per symbol maybe obtained. For n=3, each symbol under this instance of scheme C mayhave six possible states and can encode two full bits of digital data.By applying two-state cluster-wise polarization modulation, the capacityof each symbol increases to 12 states, such that each symbol can encodethree full bits of digital data.

The examples of two-state polarization modulation described above assumethat a burst may have three states with respect to a particular timeslot: absent, present with a first polarization, or present with asecond polarization different from the first polarization. In someimplementations, it may be desirable to restrict the allowed states ofsome or all bursts. For example, it may be desirable for a burst to bealways present with respect to a particular time slot, such that theburst is allowed to have only the two polarization states. In anotherexample, it may be desirable to restrict some bursts to have only theabsent and first polarization states, while other bursts are restrictedto have only the absent and second polarization states. Suchimplementations may be desirable for purposes such as synchronization,channel power uniformity, and/or coding design. Polarization modulationschemes that use more than two polarization states are also possible.

In a system employing polarization modulation, it may be desirable for atransmitter to transmit one or more bursts of predetermined polarizationto provide a polarization reference. For example, the polarization of aburst within a cluster may be assigned with respect to the first burstof the cluster. Dynamic comparison of a received burst or cluster to oneor more previously received bursts or clusters may also be used todetermine a polarization state that has been distorted duringpropagation through the transmission channel. Alternatively,polarization modulation may be applied using a channel coding scheme(such as Walsh coding) to resolve ambiguity in the polarization of thereceived bursts without the need for a polarization reference.

In other implementations of a method according to an embodiment of theinvention, width modulation is used to additionally modulate the signal,e.g., at least one element of the series of n-tuples has one of wdistinct values, such that its value indicates a width of thecorresponding burst. Such width modulation may be added to a scheme asdescribed or suggested above to increase the number of data values thatmay be transferred during a designated time period. Adding burst-wisewidth modulation to scheme A, for example, may result in a system inwhich each symbol has w^(np) different possible states.

FIG. 13G shows one example of a cluster that includes bursts that arewidth modulated. In this example, the first burst 80 of the cluster iscentered at a first frequency, the second burst 81 is also centered atthe first frequency but has a width that is twice the width of the firstburst, and the third burst 82 is centered at a second (higher) frequencyand has the same width as the first burst. The third burst may haveinformation encoded in its width or may have a preset or arbitrarywidth.

Width modulation may be applied in many different ways. For example,width modulation may be applied burst-wise. In an entirely burst-wisescheme, the width of each burst of a cluster is independently modulated,although some bursts may remain unmodulated. FIG. 13G shows an exampleof a cluster that is burst-wise width modulated.

Alternatively, width modulation may be applied other than burst-wisesuch that the width of one burst depends upon (or has a predeterminedrelation to) the width of at least one other burst. In one such scheme,all of the bursts of a cluster have the same width. It is also possibleto implement an width modulation scheme that is both burst-wise withrespect to some bursts and dependent with respect to other bursts. Twoor more bursts having a dependent width relation need not be in adjacentfrequency bands or time slots. Also, two or more bursts having adependent width relation need not have the same width (e.g. a pair ofbursts may be modulated to have related but different widths).

In scheme B as described herein, each symbol may have n^(p) possiblestates. By adding burst-wise width modulation to such a scheme, thecapability of the system may be dramatically increased to (nw)^(p)possible states, where w is the number of distinct width levelsemployed. If scheme B is applied to a particular example in which n=p=3,each symbol has 3³=27 possible states before width modulation and canencode four full bits of digital data, and after two-level burst-wisewidth modulation each symbol has (2×3)³=6³=216 possible states and canencode seven full bits of digital data. A higher number of distinctwidth values may be used to further increase the number of possiblestates per symbol.

In scheme C as described above, each symbol may have p!/(p−n)! differentstates, and if n equals p, then the possible states per symbol is n!. Byapplying burst-wise width modulation to this particular instance ofscheme C, an implementation having n!w^(n) possible states per symbolmay be obtained. For n=p=3, each symbol under this scheme may have sixpossible states and can encode two full bits of digital data. Byapplying two-level burst-wise width modulation, the capacity of eachsymbol increases to 48 states, such that each symbol can encode fivefull bits of digital data.

In a system employing width modulation, it may be desirable for atransmitter to transmit one or more bursts of predetermined width toprovide a width reference. For example, the width of a burst within acluster may be assigned with respect to the width of the first burst ofthe cluster. Alternatively, one burst within a sequence of clusters mayserve as a reference for the other bursts in the sequence.

It should be understood that width modulation may also be applied in acluster-wise fashion as described above and illustrated in FIGS. 13B,13D and 13F. In this embodiment, the bursts of the second cluster eachhave the same frequency as the corresponding one of the first clusterbut a different width. In a cluster-wise scheme, the width of eachcluster may be independently modulated, or some clusters may remainunmodulated. Width modulation may also be applied other thancluster-wise such that the width of one cluster depends upon (or has apredetermined relation to) the width of at least one other cluster.

From the above description, it is useful to note that any of thesesupplemental modulations may be combined to yield even more advancedmodulation schemes. For example, one implementation may use burst-wiseamplitude modulation combined with cluster-wise polarity modulation;another may use burst-wise polarity modulation combined with burst-wisewidth modulation; yet another may use burst-wise amplitude modulationcombined with burst-wise width modulation and cluster-wise polaritymodulation. In general, increasing the complexity of the waveformincreases the number of possible states, thus improving systemperformance while increasing system complexity.

In further implementations of a method according to an embodiment of theinvention, channel information may be encoded into intervals betweenbursts and/or between clusters of bursts. FIG. 14 shows one example ofsuch a scheme in which symbols for two different logical channels aretransferred over the same physical channel at different times. The upperdiagram illustrates a sequence of clusters [A-1 and A-2] transmittedover a first time interval on the first logical channel, which ischaracterized by an interval of one time slot between consecutivebursts. The lower diagram illustrates a sequence of clusters [B-1 andB-2] transmitted over a second time interval on the second logicalchannel, which is characterized by an interval of two time slots betweenconsecutive bursts. A receiver may be configured to identify theparticular logical channel associated with a received sequence ofclusters. Alternatively, a receiver may be configured to ignore all buta limited set (e.g. of one or more) of logical channels.

In some systems, the same physical channel may carry more than onelogical channel at the same time. For example, different logicalchannels that carry bursts during the same time interval may bedistinguished by the use of different frequencies and/or differentcombinations of frequencies. In a system in which transmission of burstsover different logical channels may be synchronized, each logicalchannel may also be distinguished by the number of time slots betweenconsecutive bursts of a cluster. FIG. 15 shows one such example in whichtwo logical channels are configured differently in terms of frequencyand timing. In another scheme, the number of time slots betweenconsecutive bursts of a cluster is a different prime number for eachlogical channel.

In the particular examples of FIGS. 14 and 15, the quiet time betweenclusters is the same on each logical channel, although in other schemesthis period may vary from one logical channel to another. In a furtherexample of a scheme including channelization, fewer than all of thepairs of consecutive bursts of a cluster (e.g. only the first and secondbursts) are separated in time. In a yet further example of such ascheme, a width of one or more of the bursts of a cluster may identifythe corresponding logical channel.

FIG. 16 shows a block diagram of a transmitter 100 according to anembodiment of the invention. Encoder 200 receives a data signal S100that includes ordered data values (i.e. ordered in time and/or space)and outputs a symbol stream S150 based on signal S100 to signalgenerator 300. Specifically, encoder 200 maps ordered sets of m datavalues to corresponding symbols, each symbol including a series of pordered n-tuples. Based on symbol stream S150, signal generator 300outputs a modulated signal S200 that includes clusters of bursts (e.g.ultra-wideband bursts). In embodiments applying additional modulations(e.g., one or more of polarity, amplitude, width and polarization), theencoder preferably encodes the additional modulation into the symbolstream S150.

FIG. 17 shows a block diagram of an implementation 150 of transmitter100 that includes a signal launcher 450 having sufficient instantaneousbandwidth to transfer the desired waveform. Signal launcher 450, whichtransfers modulated signal S200 to the transmission medium, may includeone or more elements such as filters and impedance-matching components(e.g. coils or transformers) or structures. Implementations of signallauncher 450 may also include one or more amplifiers (e.g. poweramplifiers) for such purposes as increasing signal level.

For wireless transmission of clusters, signal launcher 450 may alsoinclude an antenna. In certain cases, the antenna may be embedded into adevice that includes transmitter 100 or even integrated into a package(e.g. a low-temperature co-fired ceramic package) that includescomponents of transmitter 100 and/or signal launcher 450.

For transmission of clusters through a conductive medium (e.g. a wire,cable, or bus having one or more conductors, a conductive structure,another conductive medium such as sea or ground water, or a series ofsuch conductors), signal launcher 450 may include one or more elementssuch as components for electrostatic protection (e.g. diodes), currentlimiting (e.g. resistors), and/or direct-current blocking (e.g.capacitors).

For transmission of clusters through an optical medium (e.g. one or moreoptical fibers or other transmissive structures, an atmosphere, avacuum, or a series of such media), signal launcher 450 may include oneor more radiation sources controllable in accordance with the clustersto be transmitted such as a laser or laser diode or other light-emittingdiode or semiconductor device.

FIG. 18 shows a block diagram of an implementation 110 of transmitter100 that includes an implementation 210 of encoder 200 (having a mapper250 and a serializer 400) and an implementation 301 of signal generator300. Mapper 250 receives an m-unit parallel data signal S110 andproduces a corresponding (n×p)-unit parallel encoded signal according toa predetermined mapping. For example, mapper 250 may be constructed toreceive an m-bit parallel data signal and produce a corresponding(n×p)-bit parallel encoded signal.

In one implementation, mapper 250 may include a lookup table that mapsan m-unit input value to an n×p-unit output value. Alternatively, mapper250 may include an array of combinational logic that executes a similarpredetermined mapping function. In another application, thepredetermined mapping function applied by mapper 250 may be changed fromtime to time (e.g. by downloading a new table or selecting between morethan one stored tables or arrays). For example, different channelconfigurations (e.g. different sets of frequency bands) may be allocatedin a dynamic fashion among implementations of transmitter 100 that sharethe same transmission medium.

Serializer 400 receives the (n×p)-unit parallel encoded signal andserializes the signal to output a corresponding n-unit (e.g. n-bit)implementation S160 of symbol stream S150 to signal generator 301 (e.g.at a data rate that is p or more times higher than the data rate of theparallel encoded signal). Signal generator 300 outputs a modulatedsignal S210 based on symbol stream S160.

FIG. 19 shows an implementation 410 of serializer 400 that includes nshift registers 412. Upon assertion of a common load signal (not shown),each shift register 412 stores a different p-unit coset of the n×p-unitencoded signal. In one example, the p units stored in each shiftregister 412 are then shifted out (e.g. according to a common clocksignal) as a series of p n-tuples to signal generator 301.

FIG. 20 shows another implementation 420 of serializer 400 that includesan n×p-unit shift register 422. Upon assertion of a load signal (notshown), shift register 422 stores an n×p-unit string of values (e.g. asoutputted by encoder 210). Each of the n-unit cosets of this string isthen outputted as an n-unit value to signal generator 301 according to aclock signal (not shown).

FIG. 21 shows a block diagram of an alternative implementation 120 oftransmitter 100. Encoder 220 outputs symbol stream S150 according todata signal S100 and a clock signal S300. Signal generator 300 receivessymbol stream S150 and outputs a corresponding modulated signal S200(e.g. as a series of clusters of ultra-wideband bursts).

FIG. 22 shows one implementation 222 of encoder 220. A counter 228receives clock signal S300 and outputs a count signal S350 having one ofp values. For example, count signal S350 may count up from 0 to (p−1),or down from (p−1) to 0, or may pass through p different states in someother fashion. Mapper 226 (e.g. a lookup table or combinatorial logicarray) receives m-unit data signal S110 and count signal S350 andoutputs a corresponding n-unit symbol stream S160 (e.g. to signalgenerator 301).

Signal generator 301 receives n-unit (e.g. n-bit) symbol stream S160 andoutputs a series of clusters of bursts (e.g. ultra-wideband bursts) overn corresponding frequency bands. Each of the n frequency bands has adifferent center frequency. In one application, the n frequency bandsare separated from each other (e.g. by guard bands), although in otherapplications two or more of the bands may overlap each other.

In one implementation, each unit of symbol stream S160 is a bit thatindicates whether or not a burst should be emitted (e.g. at apredetermined amplitude) over a corresponding frequency band during acorresponding time slot. In another implementation, a unit may have morethan two values, indicating one among a range of amplitudes at which thecorresponding burst should be emitted.

Signal generator 300 includes one or more burst generators, eachconfigured to generate a burst that may vary in duration from a portion(e.g. ½) of a cycle to several cycles. The time-domain profile of eachcycle of the burst may be a sine wave or some other waveform. In oneexample, a burst generator generates a burst as an impulse that isfiltered and/or amplified. Alternatively, a burst may be generated bygating a continuous-wave signal. For example, a burst generator mayinclude a broadband oscillator with controllable bandwidth. Signalgenerator 300 may include burst generators of the same configuration orburst generators according to two or more different configurations.Example configurations for a burst generator include the following:

1) A circuit or device that produces a fast edge or pulse and isfollowed by a bandpass filter. The circuit or device that produces thefast edge or pulse generates a waveform with broadband spectral content,and the filter selects the frequency band over which transmission of theburst is desired. Examples of circuits or devices that produce a fastedge or pulse include high-speed logic gates such as ECL(emitter-coupled logic) and PECL (positive ECL). One suitableconfiguration may include a ring oscillator (e.g. as a free-runningoscillator with a gate on its output). Such circuits or devices may alsoinclude avalanche transistors, avalanche diodes, and/or step recoverydiodes. Examples of suitable filters may include cavity filters, surfaceacoustic wave (SAW) filters, discrete filters, transmission linefilters, and/or any other RF filter technique. In this case, the filtercontrols the relationship between energy and frequency within the band,and also establishes the roll-off profile of energy outside the band.

2) A tunable oscillator followed by a switching device. The tunableoscillator establishes the center frequency of the burst. The tunableoscillator can be any tunable source of continuous-wave RF energy, suchas a voltage-controlled oscillator, a YIG (yttrium-indium garnet)-tunedoscillator, a dielectric resonator oscillator, a backward waveoscillator, and/or a oscillator circuit including a reflex klystron,magnetron, or Carcinotron. The switching device sets the width of theburst, which defines the bandwidth of the spectral content. Suitableswitching devices may include mixers, solid-state RF switches,laser-controlled RF switches, plasma-based RF switches, and/or switchesthat utilize an electron beam.

3) A semiconductor solid-state oscillator that produces a frequencyburst in response to a pulsed control voltage. The pulsed controlvoltage may be provided by any circuit or device capable of delivering apulse with the desired burst width and amplitude. In order to provide afaster on/off transition, the control voltage may be biased with a DClevel that is under the oscillation threshold, such that application ofthe pulse raises the voltage over the oscillation threshold and causesthe device to oscillate for the duration of the applied pulse. Examplesof suitable solid-state oscillators may include Gunn devices, IMPATT(impact ionization avalanche transit time) diodes, TRAPATT (trappedplasma avalanche-triggered transit) diodes, and/or BARITT (barrierinjection transit-time) diodes.

4) A thermionic oscillator that produces a frequency burst in responseto a pulsed control voltage. The pulsed control voltage may be providedby any circuit or device capable of delivering a pulse with the desiredburst width and amplitude. Examples of control voltages include a gridvoltage, a body voltage, or a reflector voltage. In order to provide afaster on/off transition, the control voltage may be biased with a DClevel that is under the oscillation threshold, such that application ofthe pulse raises the voltage over the oscillation threshold and causesthe device to oscillate for the duration of the applied pulse. Examplesof suitable thermionic oscillators may include backward waveoscillators, Carcinotrons, magnetrons, and/or reflex klystrons.

FIG. 23 shows an implementation 302 of signal generator 301 thatincludes a trigger generator 320 and a set of n burst generators 330. Asshown in FIG. 24, trigger generator 320 generates trigger pulses on nindependent trigger signals according to the elements of the n-tuples ofthe symbol to be transmitted. In this example, each of the n burstgenerators 330 is configured to emit a burst upon receiving a triggerpulse. In other implementations, a burst generator may be configured toemit a burst upon receiving a rising edge or a falling edge or upon someother event (which trigger pulse, edge, or other event may be electricaland/or optical). Also in this particular example, each burst generator330 is configured to emit bursts that occupy a different frequency bandthan bursts emitted by other burst generators 330. Each burst generator330 may be configured to emit bursts of constant time duration, or oneor more of generators 330 may be configured to emit bursts of varyingtime durations.

FIG. 25 illustrates that the outputs of burst generators 330 may besummed (e.g. by summer 242 of implementation 452 of signal launcher 450)before radiation (e.g. by an antenna 244) and may also be amplified(e.g., by power amplifier 246) if desired. As shown in FIG. 26, inanother implementation 303 of signal generator 302, the outputs of burstgenerators 330 are summed (e.g. by a summer) within the signal generator303. Also in another implementation, the outputs of burst generators 330are at baseband and may be upconverted (e.g. using a mixer and localoscillator) individually and/or collectively (e.g. after summing).

FIG. 26A shows an implementation 302A of signal generator 302 thatincludes implementations 332 of burst generator 330 that are constructedto produce bursts that are modulated in amplitude, polarity, and/orwidth. In this embodiment, the trigger generator 320 receives the symbolstream S160 and includes control circuitry for trigger generation. Thetrigger generator 320 maps the input symbol stream S160 (multiple seriesof n-tuples) to a combination of burst frequencies and the additionalmodulation (e.g., polarity, amplitude, width). In turn, the triggergenerator 320 outputs a respective trigger signal and a respectivemodulation control signal to each of the burst generators 332. Themodulation control signal instructs the burst generator 332 to modulatethe burst generated with the additional modulation. For example, in oneembodiment, the modulation control signal indicates the appropriatepolarity (e.g., positive or negative) of the triggered burst in order toprovide a burst-wise polarity modulation such as illustrated in FIG.13A. In another embodiment, the modulation control signal indicates theappropriate amplitude (one of two or more preselected amplitude levels)of the triggered burst in order to provide a burst-wise amplitudemodulation such as illustrated in FIG. 13C. In another embodiment, themodulation control signal indicates the appropriate width of thetriggered burst in order to provide a burst-wise width modulation (oneor two or more preselected burst widths or durations) such asillustrated in FIG. 13G. In further embodiments, the modulation controlsignal indicates one or more of the appropriate polarity, amplitude,width or other additional modulation on a burst-wise basis. For theseimplementations, the control circuitry signals can be thought asdifferent polarity/different amplitude levels/different widths and theburst generator in turn outputs the signal of setpolarity/amplitude/width.

FIG. 26B shows an implementation 303A of signal generator 303 in whichthe output of the burst generators 332 are summed (e.g., by a summer)within the signal generator 303A similar to the embodiment of the FIG.26. It is also understood that the outputs of the burst generators maybe summed (e.g. by summer 242 of implementation 452 of signal launcher450) before radiation (e.g. by an antenna) and may also be amplified(e.g., by a power amplifier) if desired similar to the embodiment ofFIG. 25.

Depending on the type of additional or supplemental modulation to beadded to the signal generated by the signal generators 302A and 303A,the burst generators 332 may include different components. For polaritymodulation, such a burst generator 332 may include a controllable devicesuch as a double-balanced diode mixer. For amplitude modulation, such aburst generator 332 may include a controllable device such as adouble-balanced mixer, a controllable or programmable attenuator, or avariable-gain amplifier. For width modulation, such a burst generator332 may include a controllable switch (e.g., a Hittite GaAs switchcommercially available from Hittite Microwave Corporation of Chelmsford,Mass. or M/A-Com switches commercially available from M/A Com of Lowell,Mass.) to gate the burst at the appropriate duration. A burst generatormay be used to apply one or more modulations burst-wise and/or to applythe same modulation or modulations to a string of two or more adjacentbursts.

FIG. 27 shows an implementation 304 of signal generator 300 thatincludes an oscillator 340 and a gate 368. Oscillator control logic 360,which may include a trigger generator such as trigger generator 320,outputs a frequency control signal S310 and an oscillator gate controlsignal S320 that are based on symbol stream S150. Frequency controlsignal S310 may include a set of trigger signals, e.g. as shown in FIG.25. Oscillator 340, which may be a tunable oscillator as describedherein, is tunable to emit waveforms over different frequency bands atdifferent times according to frequency control signal S310. For example,oscillator 340 may be a frequency agile source whose output may bechanged from one frequency band to another between bursts. Gate 368 mayinclude a switching device as described above, a mixer, a diode, oranother suitable gate. As shown in FIG. 28, the output of gate 368 maybe amplified (e.g. by a power amplifier 246 or by a controllable poweramplifier 248 as shown in FIG. 29) before radiation.

Oscillator gate control signal S320 may control such features as burststart time, burst duration (i.e. width), and burst polarity. In someimplementations, the output of oscillator 340 may be at baseband and maybe upconverted (e.g. using a mixer and local oscillator).

In embodiments providing an additional burst-wise or cluster-wisemodulation, such as illustrated in FIGS. 13A,13B and 13G, the oscillatorgate control signal S320 may be used to signal to the gate 368 to selectone of two or more different widths (durations) and/or polarities. Thus,in a general sense, the oscillator gate control signal S320 may functionsimilarly to the modulation control signals of FIGS. 26A and 26B.

In some applications, an element of a symbol may indicate a rising orfalling frequency. In one such case, oscillator 340 is controlled (e.g.via frequency control signal S310) to emit a waveform whose frequencychanges accordingly. Such an implementation may also include a gate(e.g. gate 368) that is controlled (e.g. via oscillator gate controlsignal S320) to output a burst having a corresponding rising or fallingfrequency. Such ‘chirping’ techniques may be used in combination withone or more modulation schemes as described above.

In some applications, a polarization of the transmitted signal may becontrolled according to symbol stream S150, e.g. within signal launcher450. As shown in FIG. 29, an implementation 362 of oscillator controllogic 360 may output a launcher control signal S330 to control suchparameters as burst amplitude, duration (i.e. width), and polarization.Thus, similar to the modulation control signals of FIGS. 26A and 26B,the launcher control signal S330 may be used to implement additionalburst-wise or cluster-wise modulation.

FIG. 29A illustrates another implementation of a signal generator 308further including a modulator 378 coupled to the output of the gate 368,which produces the modulated signal S200. In this embodiment, additionalmodulation is added on a burst-wise or cluster-wise basis to the outputsignal. The components of the modulator 378 depend on the type ofadditional modulation (e.g., one or more of polarity, amplitude, andwidth) to be added to the signal, such as those described with referenceto FIGS. 26A and 26B. In one example, the oscillator gate control signalS320 controls the gate 368 which defines the burst duration (width)while the modulator control signal S330 controls the modulator 378 whichdefines the polarity of the burst to add polarity modulation to thetransmitted bursts. In this example, a double balanced diode mixer canprovide the necessary polarity control.

FIG. 29B shows another implementation 130 of transmitter 100. In thisimplementation, a digital-to-analog converter (DAC) 310 is used togenerate bursts from symbol stream S150 as desired waveforms occupyingparticular frequency bands at particular times. Thus, the waveform isgenerated in the digital domain and realized in the analog domain usingthe DAC 310. As described above, the encoder maps the bit stream (datasignal S100) to several series of ordered n-tuples (symbol stream S150).In other implementations, DAC 310 may also receive modulation controlinformation (e.g. from encoder 200) to control encoding of informationinto the polarity, amplitude, and/or width of bursts (whether burst-wiseor otherwise).

In another implementation, FIG. 30 illustrates another variation of atransmitter including a signal generator 316 receiving the symbol streamS160 and outputting the modulated signal S200 to a signal launcher 472.In this implementation, an additional or supplemental modulation isadded on a cluster-wise basis, e.g., polarity, width or amplitudemodulation (see FIGS. 13B and 13D). Rather than the trigger generator328 sending a modulation control signal to each burst generator 330 suchas illustrated in FIGS. 26A and 26B, the modulation control signal issent to the modulator 382 after the bursts have been generated (e.g., atburst generators 330) and summed, but prior to being launched. FIG. 30is similar to that of FIG. 26A except the appropriate modulation (e.g.,polarity, width, amplitude) of the individual burst generators in notcontrollable. Thus, the entire cluster is modulated (cluster-wisemodulation), rather than individual bursts within a cluster. In animplementation using amplitude modulation, the modulator 382 comprises adevice that selects the amplitude of the bursts of the cluster. In animplementation using width modulation, the modulator 382 comprises adevice that gates the bursts of the cluster to modulate burst width.

In an implementation using polarity modulation, the modulator 382comprises a polarity converter, such as illustrated in FIG. 30A. FIG.30A identifies one implementation of the polarity converter 379 for themodulator 382, which uses a parallel set of amplifiers 252 and 250, oneof which is inverted 252. Following the 2 amplifiers, switch 254 is usedto select the desired polarity signal to continue to the signallauncher. The switch 254 may be implemented in a variety of ways asknown in the art such as a Hittite GaAs switch or M/A-Com Switches.

In FIG. 31, an implementation of a transmitter for generating asignaling having an additional polarization modulation on aburst-by-burst or burst-wise basis is illustrated according to oneembodiment of the invention. An example of a cluster includingburst-wise polarization modulation is illustrated in FIG. 13F. In thisembodiment, the signal generator 318 includes control circuitry fortrigger generation 329, two different sets of burst generators 333 and334, and combiners 335. The trigger generator 329 maps input symbolstream S160 to a combination of burst frequencies and polarization(e.g., vertical, horizontal, left-hand circular, right-hand circular,etc.). In turn, the circuitry sends trigger signals to each of the burstgenerators 333 and 334 with associated polarization. The output of the Nand M burst generators is summed and presented to one or more signallaunchers 474, 475 of orthogonal polarization with sufficientinstantaneous bandwidth to transmit the desired waveform. Amplifiers 246may be used to increase the signal level, if required. One variation onthis is to synthesize the desired waveform at a lower frequency and thenupconvert the waveform to a higher frequency. Thus, the output of eachof a separate series of burst generators 333 and 334 is summed andoutput to a respective signal launcher, the signal launcher forlaunching the signal having an associated polarization that is differentfrom the polarization of the other signal launcher. By controlling whichbursts are routed to which signal launcher 474 and 475, the polarizationof individual bursts and/or entire clusters is controllable. In thisembodiment, it is unnecessary to transmit a polarization control signalfrom the trigger generator 329, since the trigger generator 329 simplydirects the appropriate trigger signal to the appropriate burstgenerator 333 or 334 to select the polarization. It is noted thatalthough only two groups of burst generators and signal launchers areillustrated, it is understood that additional signal launchers andgroups of burst generators may be added for additional polarizationmodulation options.

An alternative implementation of the transmitter of FIG. 31 isillustrated in FIG. 31A. In this transmitter, oscillator control logic369 maps input symbol stream S150 to a combination of bursts andpolarization. Unlike the embodiment of FIG. 31, the desired waveform isgenerated by rapidly tuning frequency agile sources. The frequency agilesources, labeled ‘oscillator’ 340 in the diagram, can change from onefrequency to another between bursts within the cluster of bursts. Gates368 are controlled by the oscillator control logic 369 are used todefine the duration (width) of the bursts within the cluster of bursts.The output of the gates 368 is presented to one or more signal launchers456 and 457 of orthogonal polarization with sufficient instantaneousbandwidth to transmit the desired waveform, where it may be amplified,if required. Thus, the transmitted includes separate paths to separatesignal launchers, each signal launcher for launching signaling atpolarizations that are different from each other. One variation on thisis to synthesize the desired waveform at a lower frequency and thenupconvert the waveform to a higher frequency.

Another approach to construct the desired burst-wise polarizationmodulation waveform is to generate it in the digital domain and realizeit in the analog domain using a Digital-to-Analog-Converter (DAC) asshown in FIG. 31B. Symbol stream S150 enters signal generator 321, wherethe symbol encoder 323 maps the bit stream to a series of orderedn-tuples. Entering the DACs 325 and 326 are controls from the symbolencoder 323 for timing, polarization and frequency. The DACs 325 and 326in turn generate the required series of frequency bursts with timinginformation. The output of the DACs may be amplified if required andthen presented to one or more signal launchers 478 and 479 of orthogonalpolarization with sufficient instantaneous bandwidth to transmit thedesired waveform. A variation on this is to synthesize the desiredwaveform at a lower frequency and then upconvert the waveform to ahigher frequency. Similar to FIGS. 31 and 31A, multiple paths directbursts to one of multiple signal launchers 478 and 479 which eachtransmit signaling at a different polarization. Thus, individual burstsand/or entire clusters may be modulated in polarization based upon whichpath (which DAC 325 and 326) the symbol encoder 323 selects to generatethe burst.

Another implementation of a transmitter which includes polarizationmodulation on a cluster-wise basis as an additional modulation isillustrated in FIG. 31C. An example of clusters of bursts includingcluster-wise polarization modulation is illustrated in FIG. 13G. Thetransmitter of FIG. 31C is similar to the transmitter of FIG. 31 exceptthere are fewer burst generators, e.g., there is only one set of burstgenerators 330 whose outputs are summed together (e.g., at summer 335).Thus, this embodiment offers some added simplicity relative to thetransmitter of FIG. 31. To accommodate this, switch 256 is locatedbetween the summer 335 and the signal launchers 480 and 481. The switch256 is controlled by the modulation control signal (e.g., a polarizationcontrol signal) coming from the trigger generator 332 a and informs theswitch 256 which polarization the cluster of bursts should be, thusconnecting the switch 256 to the appropriate signal launcher 480, 481.Again, each of the signal launchers 480 and 481 launches signaling atdifferent polarizations. The switch 256 may be implemented in a varietyof ways as known in the art such as using a Hittite GaAs switch or usingM/A-Com switches.

Another variation of a transmitter for transmitting signaling withpolarization modulation on a cluster-wise basis is illustrated in FIG.31D. The transmitter of FIG. 31D is similar to that of FIG. 31A exceptthere are fewer oscillators and gates. That is, rather than usingredundant sets of oscillators 340 and gates 368, the output of a singleoscillator 340 and gate 368 is switched between one of multiple signallaunchers (e.g., signal launchers 482 and 483), each signal launcher forlaunching signaling at a different polarization. To accommodate this,switch 258 is located between gate 368 and the signal launchers 482 and483. The switch 258 is controlled by a modulation control signal (e.g.,a polarization control signal) coming from the oscillator control logic370 and informs the switch 258 which polarization the cluster of burstsshould be (e.g., based upon an element of a given n-tuple), thusconnecting the switch 258 to the appropriate signal launcher 482, 483.The switch 258 may be implemented in a variety of ways as known in theart such as using a Hittite GaAs switch or using M/A-Com switches.

According to embodiments utilizing additional or supplementalmodulations to encode additional information into the transmittedclusters (such as described with reference to FIGS. 13A-13G), modulationcontrol information may be encoded in several different ways. In somearrangements, information for modulation control may be included in thevalue of the element that corresponds to a burst to be modulated. Forexample, one or more bits of the value of an element of an n-tuple maybe used to control one or more modulation modes of a burst thatcorresponds to the element. In such embodiments, the modulation may beencoded into a given symbol (e.g., an ordered series of n-tuples) duringT100 of FIG. 8.

In one such scheme for burst-wise width modulation, one bit of theelement value provides the trigger signal and the other bits of theelement value indicate the burst width. In another such scheme,different bits of the modulation control portion of the element valuemay control different modulation modes. For example, one bit mayindicate polarity of the burst, while other bits indicate the amplitudeof the burst.

Alternatively, information for modulation control may be included in thevalue of an element that is different from the element that correspondsto a burst to be modulated. For example, one of the elements of ann-tuple may be used to control the modulation of one or more bursts thatcorrespond to other elements of the n-tuple. In one such scheme, oneelement of each n-tuple controls the modulation of all of the bursts inthe corresponding time slot (e.g. either individually or collectively),while the other elements of the n-tuple indicate the frequencies of themodulated bursts.

As a further alternative, information for modulation control may beprovided in addition to the ordered series of n-tuples. For example, oneor more bits of the data stream to be transmitted may be used to controlthe modulation of all of the bursts in a cluster (or a predeterminedsubset of the bursts). In another example, each of p bits of the datastream to be transmitted (or each of p groups of bits of the datastream) may be used to control the modulation of all bursts occurring ina corresponding time slot. In a further example, bits of the data streamto be transmitted may be used to control the modulation of individualbursts of a cluster. For a scheme in which each time slot has exactlyone burst, for example, each of p bits of the data stream may be used tocontrol the modulation of a corresponding burst of the cluster. Again,in one embodiment, the additional modulation control information toaffect the additional modulation is encoded into the symbol or orderedseries of n-tuples during the encoding process (e.g., T100 of FIG. 8 andthe process of FIG. 9) performed by a transmitter.

It may be desirable to limit the spectral content of a burst. Forexample, reducing out-of-band emissions may support a more efficient useof bandwidth. Reducing out-of-band emissions may also be desired toavoid interference with other devices and/or may be required forregulatory compliance. While a filter may be used to modify the spectralcontent of a burst (as described above), in some applications it may bedesirable to modify the spectral content of a burst by controlling theshape of the burst in the time domain instead.

In one ideal system, the frequency spectrum of each burst isrectangular, and the bandwidth of the burst lies within the occupiedfrequency band. Within the frequency band, the power level is themaximum allowed by regulatory agencies; outside of the frequency band,the power level due to the burst is zero.

The frequency profile of a transmitted waveform may be controlled bycontrolling the time-dependent amplitude profile of the transmittedburst. If the time-dependent amplitude profile of the burst isrectangular, for example, the frequency content of the burst will have asine(f)/(f) profile (where f denotes frequency). In such cases, thebandwidth of the burst may extend into one or more adjacent frequencybands and may degrade performance. It may be desirable for thetime-dependent amplitude profile to have a sine(t)/(t) shape (where tdenotes time), so that a rectangular frequency profile may be created.

In a practical system, the time-dependent amplitude profile of thetransmitted burst may have a shape that is an approximation to asine(t)/(t) function. The resulting frequency spectrum may have areduction in unintentional leakage of signal energy into an adjacentfrequency band (or out of the region of spectrum allocated by aregulatory agency) as compared to a case where a rectangular amplitudeprofile is utilized. Examples of time-dependent amplitude profiles thatmay be suitable for particular applications include raised cosine,Gaussian, and low-pass-filtered rectangular pulses.

The actual technique used to generate the desired time-dependantamplitude profile of the burst may depend on the technique used togenerate the burst. In many cases, for example, a control voltage withinthe waveform generator may be tailored to provide the desired tailoredburst. One such example is the use of a mixer to switch a CW waveform togenerate the desired burst. By low-pass filtering the control signalapplied to the mixer, one can obtain a tailored time-dependent amplitudeprofile and reduced leakage of energy into adjacent frequency bands.

FIG. 32 demonstrates that a square impulse in one of the time andfrequency domains corresponds to a waveform in the other domain that hasthe shape of a sinc function. (For example, the Fourier transform may beapplied to transform a waveform in one domain to the other domain.) FIG.32A illustrates an example of a spectrum resulting from the transmission(at three different frequencies) of bursts having square profiles in thetime domain. This figure demonstrates that transmitting a burst over onefrequency band may cause emissions in neighboring frequency bands. FIG.32B illustrates an example of a spectrum resulting from the transmission(at the same three frequencies) of bursts having sinc-shaped profiles inthe time domain. This figure demonstrates that shaping the time-domainprofile of a burst may reduce emissions in neighboring frequency bands.

These figures demonstrate that spectral shaping may be based ontime-domain control of a burst profile rather than (or in addition to)the use of burst-shaping filters. In certain burst generator examplesdescribed herein, the switch or applied voltage pulse may be used tocontrol the burst shape in the time domain, thereby controlling therelationship between energy and frequency within the band and alsoestablishing the roll-off profile of energy outside the band.

FIG. 33 shows a block diagram of a tunable oscillator 342 according toan embodiment of the invention. Oscillator 342 may be used as oscillator340 in an implementation of signal generator 300 as shown, e.g., inFIGS. 27-29, 29A, 31A and 31D. In combination with a suitable switchingdevice (e.g. a gate), oscillator 342 may also be used as burst generator330 in other implementations of signal generator 300.

Oscillator 342 includes selectable delay lines 470, which introducedelays of different periods. Such delay lines may include analog delayelements (e.g. inductors, RC networks, long transmission lines) and/ordigital delay elements (e.g. inverters and/or other logic elements orgates). A common logic circuit 370 is coupled to the output terminal ofeach selectable delay line 470. Common logic circuit 370, which includesone or more logic gates, changes the state of its output signalaccording to a state transition at one of its inputs and may or may notinvert the received state transition depending on the particular circuitconfiguration. Each of selectable delay lines 470 is selectable viafrequency control signal S320 such that only one receives an outputsignal from common logic circuit 370 during any time period. It may bedesirable in some implementations to buffer the output of oscillator 342before connection of oscillator output signal S402 to a load.

In some implementations, a selectable delay line 470 may include aportion of the path that couples the selectable delay line to commonlogic circuit 370, with the length and/or character of such portionbeing designed to introduce a desired propagation delay or other effect.In other implementations, the delay (and/or the delay difference betweendelay lines) introduced by such paths may be considered negligible.

A control circuit or device (such as oscillator control logic 360)provides frequency control signal S320 to control the frequency of theoscillator's output. For example, frequency control signal S320 may be afunction of an n-tuple that indicates a burst occupying a particularfrequency band. For at least some implementations of oscillator 342, thefrequency of oscillator output signal S402 may be changed at every cycleof the oscillation.

FIG. 34 shows a block diagram of an implementation 344 of oscillator342. Each selectable delay line 472 includes an inverting selectorportion 282 (e.g. a NOR gate) and a delay portion 292 having an evennumber of inverters in series. Common logic circuit 372 is anoninverting selector (e.g. an OR gate). In this case, the lines offrequency control signal S322 are active low.

FIG. 35 shows a block diagram of an implementation 346 of oscillator342. Each selectable delay line 474 includes a noninverting selectorportion 284 (e.g. an AND gate) and a delay portion 292 having an evennumber of inverters in series. Common logic circuit 374 is an invertingselector (e.g. a NOR gate). In this case, the lines of frequency controlsignal S324 are active high.

Many other configurations are possible for oscillator 342, includingconfigurations in which each selectable delay line includes a chainhaving an odd number of inverters in series. For example, FIG. 36 showssuch a configuration 348 that includes selectable delay lines 476 havingdelay portions 294 (in this case, the lines of frequency control signalS322 are active low). The shortest path in an implementation ofoscillator 342 may include only three inversions, while the longest pathmay include an arbitrarily large odd number of inversions. Additionally,the number of different selectable delays in an implementation ofoscillator 342 may be arbitrarily large.

FIG. 37 shows a block diagram of an implementation 350 of oscillator 342in which an implementation 378 of common logic circuit 370 includes aNAND gate and an inverter. In this example, each selectable delay line478 includes a selector portion 286 (e.g. a NAND gate) and a delayportion 292 that includes a generic (e.g. analog and/or digital) delayline.

In some implementations of oscillator 342, one or more delay paths maybe further selectable. For example, FIG. 38 shows an implementation 352of oscillator 342 in which one of the delay paths includes twoindividual selectable delay lines 470.

Oscillators based on implementations of oscillator 342 as describedherein may also include oscillators that produce more than one burstsimultaneously, each such burst occupying a different frequency band.

A frequency of an oscillator may change over time. For example, thedelays introduced by the delay lines of oscillator 342 may change insome cases due to environmental factors, such as temperature or voltage,or to other factors such as aging or device-to-device variances. It maybe desirable to compensate for these variations, e.g. in order tomaintain a desired oscillation frequency.

FIG. 39 shows an implementation 356 of oscillator 342 that includesselectable adjustable delay lines 490. Each of selectable adjustabledelay lines 490 may include a controllable delay element as describedin, e.g., any one of U.S. Pat. Nos. 5,646,519; 5,731,726; or 6,054,884.Compensation circuit 495 controls a delay period of at least one ofselectable adjustable delay lines 490.

FIG. 40 shows a block diagram of an implementation 358 of oscillator 342that includes an implementation 496 of compensation circuit 495.Divide-by-N circuit 380 scales the frequency of the oscillator output tomatch that of a reference frequency oscillator 382. A phase-locked loop(or digital locked loop) 384 compares the two frequencies and outputs asignal (e.g. a voltage) according to a difference in frequency or phasebetween them. One or more digital-to-analog converters (DACs) and/orcontrollable voltage references 386 may be included to convert a digitaldifference signal into an analog signal to control a characteristic ofone or more of the adjustable delay lines 492. A DAC or controllablereference may be dedicated to one delay line or may control more thanone delay line. The DACs or controllable references may also serve tosample and hold the difference signal until a subsequent compensationoperation. In another implementation, one or more of the adjustabledelay lines are controlled digitally.

FIG. 41 shows a block diagram of an implementation 359 of oscillator 342that includes an alternate implementation 498 of compensation circuit495. This circuit includes an additional delay line 388 that isfabricated to react to environmental changes in the same way as theadjustable delay lines 492. The adjustable delay lines are thencontrolled according to a frequency or phase error in the additionaldelay line 388.

FIG. 42 shows a block diagram of an implementation 354 of oscillator 340that may be used in place of oscillator 342, e.g. in many of theapplications described herein. In this implementation, multiplexer 290applied an implementation S328 of frequency control signal S320 toprovide selection between the various delay lines 480, which may beadjustable (e.g. by a compensation circuit as described herein) but neednot include selector portions.

In some applications, it may be acceptable to run oscillator 340continuously. In other applications, it may be desirable to reduce powerconsumption by, e.g., turning on oscillator 340 (or a portion thereof,such as a compensation circuit) only a short period before transmitting.

In some implementations of oscillator 342, an oscillator output signalmay be tapped off for signal launch at more than one location. Forexample, tap off can occur at a junction where all signals are combined,or could occur outside of junctions for each signal in which the signalsmay or may not be later combined.

FIG. 43 shows a block diagram of an implementation 3591 of oscillator342. When all of the delay lines are disabled (in this example, byholding all lines of frequency control signal S320 high), the oscillatorsection (here, gates 710, 720, and 730) within common logic circuit 376may be set to run freely (in this example, with both lines of oscillatorgate control signal S329 being high). When a signal launch is desired,frequency control signal S320 selects the desired delay line and bothlines of oscillator gate control signal S329 are set low, forming acircuit including the selected delay line and output gate 740 tooscillate at the desired frequency. The lines of oscillator gate controlsignal S329 may be individually timed, or one line may be used.Similarly, the line or lines of oscillator gate control signal S329 maybe linked to (e.g. may provide timing for or may be derived from)frequency control signal S320 or may be individually timed (e.g.depending upon factors such as gate setup and hold times and concernssuch as avoiding spurious outputs). A configuration as in oscillator3591 may reduce transients due to oscillator start-up time by separatinga free-running oscillator section from the output (e.g. from the signallauncher), so that this oscillator section may be continuously runningbetween bursts or may be started-up at some time prior to the signalbeing launched.

In some applications, it may be desirable to filter the output ofoscillator 360 (e.g. to remove unwanted harmonics). Examples of suitablefilters may include cavity filters, surface acoustic wave (SAW) filters,discrete filters, transmission line filters, and/or any other RF filtertechnique.

Implementations of oscillator 360 as described above may be fabricated(e.g. in whole or in part) in application-specific integrated circuits(ASICs) using one or more known techniques such as ECL, PECL, CMOS, orBiCMOS and materials such as SiGe, GaAs, SiC, GaN, ‘strained silicon’,etc.

FIG. 44 shows a receiver 400 according to an embodiment of theinvention. Signal detector 410 receives a received signal (e.g. afteramplification and/or filtering) and outputs an ordered series ofn-tuples. Decoder 421 receives the ordered series of n-tuples andoutputs a corresponding ordered set of data values. Decoder 421 may alsoperform digital signal processing operations on the series of n-tuples(e.g. filtering operations).

FIG. 45 shows a block diagram of a burst detector 430 suitable for usein signal detector 410. Filter 440 (e.g. a bandpass filter) passesenergy within a particular frequency band. Edge detector 455 detects arising edge of a signal received within the corresponding frequencyband. Signal detector 410 may include a parallel arrangement of severalburst detectors, each configured to detect bursts on a differentfrequency band.

FIG. 46 shows a block diagram of an implementation 455 a of edgedetector 455. In this example, the envelope detector 510 is a square-lawdevice. For high-frequency applications, for example, the envelopedetector 510 may be a tunneling diode or similar device. The basebandoutput of the envelope detector 510 is amplified (e.g. by basebandamplifier 520) and digitized (e.g. by analog-to-digital converter (ADC)530).

In its simplest form, digitization of the baseband signal may beperformed by comparison of the signal with a reference voltage (e.g.thresholding). For example, FIG. 47 shows a block diagram of such an ADC532 including a comparator 540. Depending on the particular application,other suitable ADCs may include multi-bit parallel-encoding (flash),successive-approximation, dual-slope, digital-ramp,delta-sigma-modulation, or other configurations.

FIG. 48 shows an implementation 401 of receiver 400 that includes animplementation 413 of signal detector 410. Signaling is received atantenna 590 and coupled to the signal detector 413. Optionally, thereceived signaling may be amplified (e.g., by LNA 550) before forwardedto the processing circuitry. This signal detector 413 includes aparallel arrangement of implementations 432 of burst detectors 432, theoutputs of which are coupled to the decoder 421. Each burst detector 432includes a filter 440 and edge detector 455. As shown in this example, aburst detector 432 may include other processing blocks such as low-noiseamplifiers (LNAs). It is noted that depending on the specificimplementation, the one or more of the amplifiers (e.g., LNAs 550, 560and 570) are optional.

FIG. 49 shows a block diagram of another implementation 455 b of edgedetector 455. In this example, a correlator 610 receives the filteredsignal and correlates it with a template to produce a correspondingbaseband signal, which is amplified (e.g. by baseband amplifier 520) anddigitized (e.g. by ADC 530).

FIG. 50 shows an implementation 402 of receiver 400 that includes animplementation 414 of signal detector 410. This signal detector includesa parallel arrangement of implementations 434 of burst detector 430 thatinclude correlators 610, each of which may apply a different template totheir input signals. In this case, each burst detector 434 also includesa LNA 560 upstream of the correlator 610 that serves as a filter. Also,in this case, a baseband amplifier 520 is located between the correlator610 and the ADC 530. Again, it is noted that depending on the specificimplementation, one or more of the amplifiers (e.g., LNAs 550, 560 andamplifier 520) are optional.

As the operating speed of ADCs increases, it is also contemplated tosample the incoming signal directly and filter it after digitization.One such receiver is shown in FIG. 51. The signaling is received atantenna 590, optionally amplified (e.g., at LNA 550), converted todigital at ADC 530 and forwarded to the decoder 421. In one suchimplementation, the digitized output is filtered (e.g. by decoder 421)to determine the activity over time on each frequency band. In anotherimplementation, successive fast Fourier transforms are performed in timeon the digitized output, and the activity on each individual frequencyband is determined from the resulting spectral information.

It is also possible to divide the signal into different sections of thespectrum and then to downconvert each section separately. Afterdownconversion (e.g. using a mixer 620 and local oscillator 630 at thedesired intermediate frequency, which may differ from one frequency bandto another), the bursts may be detected using edge detection or thesignal may be sampled directly with an ADC. FIG. 52 shows a blockdiagram of an implementation 404 of receiver 400 that includes edgedetectors 455. In this implementation 416 a of the signal detector, theburst detector 435 amplifies (e.g., optional LNA 560) and filters (e.g.,filter 440) the signal prior to downconverting (e.g., using the mixer620 and local oscillator 630). The signal is then filtered (e.g., filter442), optionally amplified (e.g., LNA 570) and then forwarded to theedge detection 455. FIG. 53 shows a block diagram of an implementation405 of receiver 400 including implementation 416 b of the signaldetector including burst detectors 436 that sample each signal directlyusing an ADC. In this embodiment, each burst detector 436 optionallyamplifies (e.g., LNA 560), filters (e.g., filter 440), and downconvertsthe signal (e.g., using the mixer 620 and the local oscillator 630),then converts the signal to digital (e.g., at ADC 530).

In some applications, it may be desirable to downconvert the receivedsignal to an intermediate frequency (e.g. by mixing with a localoscillator signal) before performing further processing as describedabove, i.e., convert to an intermediate frequency prior to processingentering the signal detector. For example, the signaling is received atantenna 590, optionally amplified (e.g., by LNA 550) as needed, thendownconverted to an intermediate frequency (e.g., using the mixer 620and the local oscillator 630), before entering the signal detector.Since the received signal contains bursts having different frequencies,the output of the downconverter is at a different intermediate frequencyfor bursts of different frequencies. FIG. 54 shows one suchimplementation 406 of receiver 400 in which the downconverted signal isdivided into separate intermediate frequencies before edge detection455. FIG. 55 shows another implementation in which the downconvertedsignal is divided into separate intermediate frequencies (by mixer 620and local oscillator 630) before correlation (e.g., at correlator 612b). FIG. 56 shows a further implementation in which the downconvertedand filtered signal is digitized directly similar to the embodiment ofFIG. 51 (i.e., mixer 620 and local oscillator 630 before ADC 530).

In other embodiments, the signaling is downconverted to intermediatefrequencies prior to entering the signal detector (e.g., by the mixer620 and the local oscillator 630) and then downconverted again (e.g., bymixer 620 and local oscillator 630 b) within the individual burstdetectors of the signal detector prior to further processing. FIG. 57shows a block diagram of an implementation 409 of receiver 400 in whichan intermediate frequency signal is separated into different frequencybands before a second downconversion and edge detection 455 b within theburst detectors 435 within of signal detector 415 a. FIG. 58 shows ablock diagram of another implementation 409 a in which thetwice-downconverted signals (converted prior to entering the signaldetector 416 b and downconverted within the burst detectors 436 b) aredigitized and filtered (at ADC 530). In some applications, an increasein signal-to-noise ratio may be achieved by performing gating of thereceived signal (e.g. in combination with a receiver configuration asdescribed herein).

It is understood that in the receiver embodiments described herein,although several embodiments illustrate an antenna 590 for receiving thelaunched signaling, depending on the transmission scheme and medium, anantenna is not required. In such embodiments, a suitable receivingdevice understood for use by the transmission scheme and medium may usedin place of the antenna 590.

Many of the receivers described above may be used to properly receiveand decode signaling launched according to several embodiments of theinvention, and including signaling launched with additional orsupplemental modulations on a burst-wise and/or cluster-wise basisencoding additional information into the launched signaling, e.g.,signaling such as illustrated in FIGS. 13A-13G.

For example, according to several embodiments, the receiver 402 of FIG.50 may be used to receive signaling launched including one or moreburst-wise and cluster-wise additional modulations, e.g., polaritymodulation, amplitude modulation, and width modulation. In receiver 402,the received signal is correlated with a template waveform. Thecorrelated signal contains the additional modulation information (e.g.,polarity, amplitude and/or width) and time information and the decoder421 uses this information to reconstruct the data from the receivedwaveform. The template can be a stored waveform, or can be from areferenced burst or cluster of bursts from within the transmitted streamor transmitted at some period prior to reception. The use of atransmitted reference is advantageous because the reference travels withthe data and experiences the same distortion as the data, thus making iteasier to decipher timing, frequency, and the additional information(e.g., polarity, amplitude and width). It is noted that the template foreach correlator 610 of each burst detector 434 is different in order tocorrelate the different bursts that the transmitter may launch.Furthermore, the receiver can incorporate frequency downconversion(e.g., before entering the signal detector 414 and/or within the burstdetectors 434) as described above to permit the use of less costly,lower frequency components.

In another example, according to several embodiments, the receiver 401of FIG. 48 may be used to receive signaling launched including one ormore burst-wise and cluster-wise additional modulations, e.g., amplitudemodulation, polarity modulation and width modulation. The receivedsignal is optionally amplified via LNA 560, if necessary, and applied toa bank of filters 440. The filters 440 discriminate signal energy in thebands of interest. The filtered signal may be amplified if necessary(e.g., by LNA 570) prior to edge detection 455. The edge detection 455detects a rising edge of a signal received within the correspondingfrequency band. The edge detection 455 may also be configured to detecta polarity of the received signal. The signal contains the additionalinformation (e.g., amplitude, polarity and/or width) and timeinformation and the decoder 421 uses this information to reconstruct thedata from the received waveform (e.g., the decoder determines whichsymbol (an ordered series of n-tuples) was received for converts it tothe corresponding data). The use of absolute amplitude and/or width atthe detector to reconstruct the data contained in the burst may bedifficult as the characteristics of the propagation channel may varywith time, introducing errors. An alternative to having predeterminedamplitude/width thresholds is having the burst amplitude/width comparedwith a reference burst or cluster of bursts. This reference can be aseparate burst or cluster of bursts, or simply another burst or clusterof bursts in the transmitted stream. Alternatively, the information canbe encoded in the relative amplitudes/widths of the separate frequencybursts. Furthermore, the receiver can incorporate frequencydownconversion to permit the use of less costly, lower frequencycomponents.

In another example, according to several embodiments, the receiver 401of FIG. 51 may be used to receive signaling launched including one ormore burst-wise and cluster-wise additional modulations, e.g., polaritymodulation, amplitude modulation, and width modulation. In thesevariations, the received signal is optionally amplified by LNA 550, ifrequired, and digitized via ADC 530 and decoded in the digital domain bydecoder 421. In this embodiment, the decoder is configured to recognizeand decode the various digital representations of the launched burstshaving the additional information modulation, such as polarity,amplitude and width. Again, a reference burst or cluster of bursts maybe employed in the transmitted stream or transmitted prior to receptionto aid in the determination of received burst characteristics.Additionally, the receiver can incorporate frequency downconversion topermit the use of less costly, lower frequency components.

It is noted that the receivers described above may be used to receiveand detect signaling including the additional modulation on a burst-wisebasis and/or on a cluster-wise basis.

For these receiver implementations, methods of encoding can be used toeliminate the need for a predefined reference cluster of bursts.Encoding can be done using either relative polarity, amplitude, or widthof frequency bursts within the cluster of bursts or using differentialpolarity, amplitude or width between successive clusters of bursts.

In other implementations employing additional modulation information,such as polarization information, into the launched cluster to furtherencode information, variations of the receivers presented above aredescribed. Examples of such signaling are illustrated in FIGS. 13E and13F. FIG. 60 shows an example of a receiver 409 b for receivingsignaling including burst-wise and/or cluster-wise polarizationmodulation. The receiver 409 b is comprised of multiple antennas 591 and592, optional low noise amplifiers (LNAs 550), multiple signal detectors418 a and 418 b (each signal detector including a number of burstdetectors 432 a and 432 b), and decoder 426. The burst detectors 434 ofeach signal detectors 418 a and 418 b are comprised of LNA 560 (asneeded), band-pass-filter 611, LNA 560 (as needed), and envelop detector(ED) 561. Each of the antennas 591 and 592 receives signaling having aspecified and different polarization, e.g., antennas 591 and 592 areorthogonal to each other. The received signal is amplified via the firstLNA 560, if necessary, and applied to a bank of filters. The filters 611discriminate signal energy in the bands of interest. The filtered signalmay be amplified (e.g., at LNA 560) if necessary. The signal containstime information, and together with the other polarization signaldetectors, and decoder 426 uses this information to reconstruct the datafrom the received waveform. The use of absolute polarization at thedetector to reconstruct the data contained in the burst may be difficultas the characteristics of the propagation channel may vary with time,introducing errors. An alternative to having predetermined polarizationsis having the burst polarization compared with a reference burst orcluster of bursts. This reference can be a separate burst or cluster ofbursts, or simply another burst or cluster of bursts in the transmittedstream. Alternatively, the information can be encoded in the relativepolarization of the separate frequency bursts. Furthermore, the receivercan incorporate frequency downconversion (e.g., before entering thesignal detectors 418 a and 418 b and/or within the burst detectors 432 aand 432 b) similar to that described above to permit the use of lesscostly, lower frequency components. It is noted that although two pathsare illustrated, i.e., two separately polarized antennas 591 and 592each coupled to a separate set of burst detectors 432 a and 432 b,additional antennas and sets of signal detectors may be implemented inorder to add further polarization variations.

FIG. 61 shows a variation of the receiver of FIG. 60 in which thereceiver 409 c includes the signal detectors 417 a and 417 b includingburst detectors 434 a and 434 b that are implemented using correlators610, rather than filters 611 and envelope detectors 561. Each correlator610 stores a given template to be correlated with the received waveform.The correlated signal contains time information and together with theother polarization signal detectors, the decoder 427 uses thisinformation to reconstruct the data from the received waveform. Thetemplate can be a stored waveform, or can be from a referenced burst orcluster of bursts from within the transmitted stream or transmitted atsome period prior to reception. The use of a transmitted reference isadvantageous because the reference travels with the data and experiencesthe same distortion as the data, thus making it easier to deciphertiming, frequency, and polarization information. Furthermore, thereceiver can incorporate frequency downconversion (e.g., before enteringthe signal detectors 417 a and 417 b and/or within the burst detectors434) to permit the use of less costly, lower frequency components.

In another embodiment, the receiver 409 d of FIG. 62 may be used toreceive and decode signaling including burst-wise or cluster-wisepolarity modulation. In this embodiment, the signal is received byorthogonal antennas 591 and 592, such as horizontal and vertical linearpolarizations, or right and left hand circular polarizations. Eachantenna provides a separate signal path to the decoder 428, a singlepath similar to the receiver of FIG. 51. In each path, the receivedsignal is amplified by LNA 550, if required, and digitized via ADC 530and decoded in the digital domain by decoder 428. In this embodiment,the decoder 428 is configured to recognize and decode the variousdigital representations of the launched bursts having the additionalpolarization modulation. Again, a reference burst or cluster of burstsmay be employed in the transmitted stream or transmitted prior toreception to aid the in the determination of received burstcharacteristics. Additionally, the receiver can incorporate frequencydownconversion to permit the use of less costly, lower frequencycomponents.

It is noted that the receivers described in FIGS. 60-62 may be used toreceive and detect signaling including the additional polarizationmodulation on a burst-wise basis and/or on a cluster-wise basis.

The use of amplifiers throughout this entire disclosure, on the receiveside, are shown in the figures primarily using low noise amplifiers(LNAs); and it is equally valid to use other types of amplifiers besideslow noise amplifiers; such as variable gain amplifiers (VGAs), rfamplifiers amplifiers, and limiting amplifiers.

In some applications, it may be desirable for a receiver as describedherein to apply a timestamp to one or more received clusters or tootherwise note the order and/or time of arrival of clusters. Forexample, such information may be applied during decoding of the receivedsymbols and/or may be applied to overcome multipath interference.Information regarding the relative time between clusters may also beused to detect empty clusters (such a technique may also be applied atthe time-slot scale to detect empty time slots). For noting order ofarrival only, the timestamp may be generated using a counter whose stateis updated (e.g. incremented) at each noted event (e.g. clusterarrival). For noting time of arrival, the timestamp may be generatedusing a clock (e.g. a counter whose state is updated according to anoscillator). For relative measurements between events, it may not benecessary to synchronize such a clock to a reference or to otherwisetake account of the clock's initial state.

At least some of the techniques for data transfer as disclosed hereinmay be embedded into highly scaleable implementations. For example, sucha technique may be applied to wireless replacement of cables fortransmission of content and/or control data. In a low-end application,this technique may be implemented to replace a cable (e.g. a UniversalSerial Bus or USB cable) linking a computer to a low-cost, low-data-rateperipheral such as a computer mouse, keyboard, or handheld gamingcontroller. In a mid-range application, the technique may be used toreplace a cable carrying video information from a computer to a monitor.In a high-end application, the technique may be scaled to replace one ormore of the cables that carry high-fidelity video and audio information(e.g. from a receiver, a set-top box, or DVD (Digital Versatile Disc)player) to a high-definition television display and audio system.

Other applications that may vary in cost and performance requirements tothose noted above include wireless computer networking, wirelesstransfer of audio data (e.g. as one or more datastreams and/or files,and in formats such as sampled (e.g. WAV) and/or compressed (e.g. MP3)),wireless transfer of image data (e.g. from a digital still camera orother device including one or more CCD or CMOS sensors, and inuncompressed or compressed (e.g. JPEG, JPEG2000, PNG) format), andwireless replacement of cables transmitting such formats or protocols asEthernet, USB, IEEE 1394, S-video, NTSC, PAL, SECAM, and VoIP (Voiceover IP).

In addition to many office and consumer entertainment applications, suchcable replacement may be applied to control systems in industry and athome (e.g. thermostatic control); in automobiles and other vehicles; andin aircraft applications (e.g. for control systems and also to supportnetworking applications such as passenger e-mail). Therefore, systems,methods, and apparatus for data transfer as disclosed herein may beimplemented to suit a wide range of different latency, performance, andcost requirements.

One problem that may be encountered when using existing methods ofwireless data transfer is an inability (e.g. insufficient datathroughput rate) to support the data rate or latency requirements for ademanding application such as real-time video display. As noted above,systems, methods, and apparatus for data transfer as disclosed hereinmay be implemented to transfer data at very high rates. In one suchapplication, a set-top box includes an apparatus for data transfer asdisclosed herein which may be used to transmit a video signal wirelesslyto a television display (e.g. a flat-panel display). One benefit thatmay be realized from a very high data rate in such an application is anability to update the displayed picture (e.g. in response to the userchanging the channel) in real time, rather than after a lag as might besuffered in a low-data-rate system that requires buffering to maintainthe displayed picture.

Signal source identification mechanisms may be applied within systems,methods, and apparatus for data transfer as disclosed herein to supportnetworking applications. An identifier such as a serial number may behard-coded into a transmitter or transceiver (e.g. during manufacture orinstallation), or the identifier may be assigned or updated by theapplication during use. The identifier may be transmitted in the samemanner as other data to be transferred (e.g. within a protocol or otherhigher-layer abstraction), or the identifier may be distinguished fromother data within the physical layer by using features discussed hereinsuch as logical channelization and/or unused symbol states.Communications applications in which source identification may be usefulinclude directing communications within piconets, mesh networks, andmultihop networks (e.g. including repeaters); distributed sensornetworks for industry and military; encrypted and other securecommunications; and selective or exclusive communication between datasources (e.g. a computer or PDA) and peripherals (e.g. a printer).

Applications for systems, methods, and apparatus for data transfer asdisclosed herein may include location and position determination tasks.These tasks may include ranging and triangulation operations. A rangingsignal may include a burst, a stream of bursts at different frequenciesand/or different times, or a cluster or group of clusters.Ultra-wideband signals having extremely short bursts (e.g. durations ofone nanosecond or less) are especially well-suited to such applicationsbecause the shortness of the bursts corresponds (under ideal conditions)to high spatial resolutions (e.g. down to the order of one centimeter).Better spatial resolution may also be achieved by transmitting theranging signal over a wide frequency range (e.g. including bursts overmore rather than fewer frequency bands). It may be desirable for aranging signal to include signal source identification information(e.g., as described above), especially in an environment that includespotential interferers such as other transmitters.

In one example of a ranging operation, a first transceiver transmits aranging signal. A second transceiver detects the signal and transmits aresponse (e.g. a ranging signal that may include information such as thesecond transceiver's location). The first transceiver detects theresponse, notes the round-trip time of flight, removes a known latencyvalue (e.g. the propagation time within the circuits), divides by two toremove the bidirectional component, and divides by the speed of light todetermine the distance between the two transceivers. A triangulation (ortrilateration) operation may then be performed by combining thedistances obtained from at least three such ranging operations (i.e.between the first transceiver and at least three other transceivershaving known locations) to determine the first transceiver's location.

In another example of a ranging operation, a first transmitter transmitsa ranging signal that is received by three or more receivers. The timesof arrival of the signal at each receiver are transmitted to aprocessing unit (e.g. via a network), which combines the various timesof arrival and corresponding receiver locations in a triangulation (ortrilateration) operation to determine the transmitter's location. It maybe desirable in this case for the receivers to be synchronized to acommon clock.

In a variation of the ranging operation above, the ranging signalincludes a signal source identifier. Each receiver timestamps thereceived ranging signal according to the time of arrival and transmitsthe timestamped signal (including the source identifier) to theprocessing unit. Such a technique may be used to support location andposition determination for multiple transmitters. Transmitter locationand position determination may also be performed within a multihopnetwork such that the processing unit is several hops removed from thetransmitter.

At least some of the systems, apparatus, and methods of data transfer asdisclosed herein may be applied to sensor networks. In such a network, apossibly large number of sensors is deployed across an area, with senseddata being returned (possibly relayed via multihop) to a processingunit. Each sensor is configured to sense an environmental condition suchas gas concentration, radiation level at one or more frequencies orranges (e.g. charged particle, X-ray, visible light, infrared),temperature, pressure, sound, vibration, etc. A sensor may include ananalog-to-digital converter for converting data relating to the sensedcondition from analog to digital form.

A sensor network as described herein may be used for temperaturemonitoring within a facility, for an intruder alert system, or forremote monitoring of activity in an area (e.g. for military purposes).The processing unit, which calculates the state of the network from thecollective sensed data, may act accordingly or may convey the stateinformation to another unit.

Additionally, use of methods and apparatus for data transfer asdescribed herein may include applications requiring very low cost,robustness to interference and/or multipath, low probability forintercept and/or detection, and/or sensor applications (e.g. networkedor peer-to-peer). For example, low-cost sensors may permit vastdeployments for either tagging or distributed feedback systems forcommercial, industrial, and military applications. Interference andmultipath robustness may be especially useful for deployments inindustrial settings and military scenarios where jamming (intentional orunintentional) and/or reflections are likely. Low probability forintercept (both in terms of implementing special symbol codes and interms of possible operations at low emission levels) and low probabilityfor detection are critical components of covert military or sensitiveusages.

FIGS. 63 through 73 illustrate further embodiments of encoders anddecoders. FIG. 63 shows a block diagram of a multi-band transmitter 2000according to one embodiment of the invention. It comprises a triggergenerator 2020, which is coupled to a data source through data signal2010 and to one or more burst generators 2040 a through 2040 n. Theburst generators are configured to emit bursts in specific frequencybands (e.g., ultra-wideband bursts) and are connected to a summer 2050.The summer's output is coupled to the input of an optional poweramplifier 2060. Power amplifier 2060 is further connected to antenna2070.

In this embodiment, trigger generator 2020 receives a data signal 2010and encodes the received data into a sequence of trigger signals 2030 athrough 2030 n, which activate the burst generators 2040 a through 2040n at times according to the encoded data signal. Thus, in contrast toearlier embodiments, the encoder is implemented within the triggergenerator. When activated, a burst generator 2040 emits a burst in itsspecific frequency band. Summer 2050 combines the burst generatoroutputs into a signal amplified by power amplifier 2060 and radiatedthrough antenna 470. In some embodiments, burst generators are activatedby a single-bit trigger signal. In other embodiments, burst generatorsmay be activated using multi-bit trigger signals.

FIG. 5 shows a block diagram of a multi-band receiver 2100 according toone embodiment of the invention. It comprises a low-noise amplifier(LNA) 2120 whose input is coupled to an antenna 2110 and whose outputsare connected to one or more burst detectors 2130 a through 2130 n. Theoutputs of burst detectors 2130 a through 2130 n are connected to theinputs of signal decoder 2150 through detector signals 2140 a through2140 n.

Upon detecting a burst, a burst detector 2130 a through 2130 n signalsdetection of a burst in its frequency band to attached signal decoder2150. Signal decoder 2150 decodes a sequence of detected bursts,constituting a cluster, into a data signal that is communicated to adata sink through data signal 2160.

In one embodiment, a burst detector 2130 a through 2130 n is configuredto communicate the presence or absence of a burst through detectorsignal 2140 a through 2140 n, which may be represented with a single bitof information in detector signal 2140 a through 2140 n. In otherembodiments, a burst detector 2130 a through 2130 n is configured tocommunicate other and/or additional characteristics of a detected burst,such as its amplitude, its polarity, or other characteristics know inthe art, which may be represented by one or more bits of informationcommunicated to signal decoder 2150 through detector signal 2140 athrough 2140 n. The burst detectors may be as described throughout thisspecification.

Several embodiments of the invention described herein will generally bedescribed assuming a single bit of information be exchanged between thetrigger generator 2020 and the burst generator 2040 and between theburst detector 2130 and the signal decoder 2150. Those skilled in theart will readily understand that the generic principles described hereinapply in the same way when the information exchanged consists ofmultiple bits of information. Without loss of generality, the followingdescriptions use the designator n to refer to the number of burstgenerators, as well as the number of burst detectors. Designator p isused to denote the maximum number of time slots per cluster, whiledesignator m denotes the number of bits of the data signal entering thetransmitter and the number of bits of the data signal exiting thereceiver.

Referring to FIG. 65, an embodiment of a trigger generator 2200 isillustrated, which consists of an encoder 2220, a shift register foreach frequency band (2230 a through 2230 n), and a controller 2250.Encoder 2220 encodes input data 2210 into a set of control signals thatcontrol the operation of the n burst generators attached to the serialoutput of the shift registers 2230 a through 2230 n. Upon assertion ofthe load signal by controller 2250, the shift registers 2230 a through2230 n are loaded with a set of control signals (die). Then, by shiftingthe register contents during successive clock cycles, the serial outputsof the shift registers 2230 a through 2230 n control the burstgenerators during each time slot. The serial outputs of a shift registermay comprise a single signal turning the attached burst generator on oroff, or may comprise multiple signals that control the attached burstgenerator in further ways, such as determining its phase and/oramplitude, or other characteristics of the burst generator. Aftertransmitting a cluster, the shift register outputs are configured suchthat they deactivate the attached burst generators until newly loadedwith the next cluster. This can be achieved by shifting in a constantvalue, such as 0, which deactivates the burst generators, or byincreasing the length of the shift register by one stage to load aterminal value that deactivates the burst generators. Controller 2250controls the emission of a cluster by asserting and deasserting the loadsignal and providing clock pulses to the shift registers at theappropriate times.

To transmit data, data input signals 2210 are supplied to the inputs(x_(a) . . . x_(m)) of encoder 2220 and the enable signal of the controlblock 2250 is asserted. Encoder 2220 then encodes the input into a setof burst generator control signals (d_(aa) . . . d_(pn)). Control signald_(ik) will be loaded into shift register k and will control burstgenerator k during time slot i. Depending on the burst generators,d_(ik) may comprise a single bit to activate and deactivate the burstgeneration, or may consist of multiple bits, e.g. to control theamplitude or the polarity of the generated frequency burst.

Referring to FIG. 65, controller 2250 generates the shift registerload/shift signal as well as the time slot clock for the required numberof cycles given by the number of time slots. By asserting the loadsignal attached to the shift registers 2230 a through 2230 n, andproviding a clock pulse, controller 2250 causes the shift registers toload outputs d_(aa) through d_(pn) of encoder 2220. Control signalsd_(aa) through d_(an) appear at the serial output of the shift registers2230 a through 2230 n first and control the burst generators during thefirst time slot. After loading the shift registers, controller 2250deasserts the load signal, causing the shift registers 2230 a through2230 n to shift the loaded data upon receiving clock pulses fromcontroller 2250. The controller then generates p−1 additional clockpulses to shift out the remaining control signals d_(ba) through d_(pn)stored in the shift registers. Each clock pulse marks the start of a newtime slot.

It will be understood by persons skilled in the art that controlling theshifting of the shift register by means of providing clock pulses is butone embodiment. Other embodiments, such as embodiments using an explicitshift signal to control shifting while providing clock pulsescontinuously, are equally possible.

Encoder 2220 can be implemented using a Random Access Memory (RAM), aRead-Only Memory (ROM), or a programmable ROM such as an ElectricallyErasable Programmable ROM (EEPROM) addressed by the data input (x_(a)through x_(m)). Alternatively, the encoder can be implemented as acombination of logic gates (combinational logic) whose inputs are thedata input (x_(a) through x_(m)) or by any other method known in theart. The number of data input bits (m) varies with the chosen encoding,the number of time slots (p), and the number of frequency bands (n). Thenumber of output bits (d_(aa) through d_(pn)) in one embodiment is theproduct of p and n.

In the preferred embodiment, encoder 2220 is implemented such that itcan be reconfigured during operation. For example, an embodiment usingRAM allows the transmitter 2200 to be reconfigured to use a differentcluster encoding, a reduced number of burst generators, and/or a reducednumber of time slots. This enables transmitter 2200 to adapt tointerference, for example, by avoiding the use of the frequency bandssubject to interference, or to provide different data rates at differenttimes or under different conditions.

Controller 2250 is preferably implemented as a finite state machineusing combinational logic gates and state registers, but other meansknown in the art, such as a processor and memory, are equallyapplicable.

FIG. 66 shows a control flow diagram for controller 2250 in FIG. 65. Atblock 2260, controller 2250 waits until the enable input is asserted,indicating that a data value is present on the data signal input 2210 inFIG. 65. When enable is asserted, the controller advances to block 2270,where it asserts the load output, causing the shift registers 2230 athrough 2230 n to be loaded with the output of the encoder 2220. Afterone clock cycle, the load flag is deasserted at block 2280, causing theshift registers to switch from loading mode to shift mode, and thecontroller advances to block 2290 where the controller issues p−1additional clock cycles. After the cluster is transmitted (p clockcycles later), the controller returns to block 2260, awaiting the nextdata value to be transmitted.

The loadable shift registers 2230 a through 2230 n in FIG. 65 areimplemented as known in the art. FIG. 67 shows one possibleimplementation of a parallel-to-serial shift register 2300. It consistsof p pairs of a D flip-flop and a preceding multiplexer. The shiftregister 2300 is loaded by asserting the load signal and providing aclock pulse, whereupon each D flip-flop is loaded with one of the pinputs. Deasserting the load signal and providing subsequent clockpulses causes the loaded values to be shifted to the right while a 0value into the left-most D flip-flop.

TABLE 1 shows an example of an encoding table according to oneembodiment. For this example, it is assumed that a control bit withvalue 1 causes the corresponding burst generator to emit a frequencyburst and that a control bit with value 0 causes it not to emit a burst.It is assumed that during each time slot exactly one burst generatoremits a frequency burst and that a burst generator emits only onefrequency burst during a cluster (such as in cluster 94 of FIG. 11). Itshould be understood that this is only one possible method to encodedata values and that both the encoding table may vary as well as the wayin which the burst generators are controlled.

TABLE 1 Time Time Time Slot 0 Slot 0 Slot 2 Data x₂ . . . x₀ d₀₂ . . .d₀₀ d₁₂ . . . d₁₀ d₂₂ . . . d₂₀ 0 000 100 010 001 1 001 010 100 001 2010 100 001 010 3 011 001 100 010 4 100 010 001 100 5 101 001 010 100

As a result of these assumptions, there are n! possible data values withn burst generators, or 6 distinct clusters using n=3 burst generators asshown in TABLE 1. Each of the 6 data values is presented to the encoderas a binary number of m=3 bits (x₂ . . . x₀). The encoder producescontrol signals for each burst generator k in time slot i. There are p=3time slots. These control signals d_(ik) are stored in the shiftregister. For example, to encode the data value 3, burst generator 0emits a frequency burst during time slot 0, burst generator 2 emits aburst during time slot 1, and burst generator 1 emits a burst duringtime slot 2.

FIG. 68 shows an alternative embodiment of a trigger generator. Triggergenerator 2300 comprises an encoder 2320 coupled to a time slot counter2330, and a controller 2350 controlling time slot counter 2330. Encoder2320 outputs d_(a) through d_(n) are coupled to the burst generatorsinputs and control the burst generators' operation.

To transmit a data value, the data value is provided to encoder 2320through data signal 2310 and the enable signal 2340 is asserted. Thedata value is provided to the encoder for the duration of the cluster,generally p time slots. Upon assertion of the enable input, controller2350 asserts the start signal for one clock cycle. Time slot counter2330, upon determining its start input signal asserted, counts for pclock cycles. After counting for p cycles, time slot counter 2330asserts the done signal, signaling to controller 2350 that counting hasterminated. The values counter 2330 assumes, corresponding to thecurrent time slot number, are provided to encoder 2320 as r bits.

Encoder 2320 uses data signal input 2310 and the current value of timeslot counter 2330 to determine the control signals for the n burstgenerators attached to the encoder outputs d_(a) through d_(n) for thetime slot defined by the value of the time slot counter 2330.

Encoder 2320 can be implemented using a Random Access Memory (RAM), aRead-Only Memory (ROM), or a programmable ROM such as an ElectricallyErasable Programmable ROM (EEPROM) addressed by the data input (x_(a)through x_(m)) and the time slot counter value (c_(a) through c_(r)).Alternatively, the encoder can be implemented as a combination of logicgates (combinational logic) whose inputs are the data input (x_(a)through x_(m)) and the time slot counter value (c_(a) through c_(r)), orany other way known in the art. The number of data input bits (m+r)varies with the chosen symbol encoding, the number of time slots (p),and the number of frequency bands (n). The number of counter output bitsr is given by the formula |log₂(p)|. The number of output bits in oneembodiment is the number of burst generators n. Depending on the burstgenerators, d_(ik) may comprise a single bit to activate and deactivatethe burst generation, or may consist of multiple bits, e.g. to controlthe amplitude or the phase of the generated frequency burst.

In the preferred embodiment, encoder 2320 is implemented such that itcan be reconfigured during operation. For example, an embodiment usingRAM allows transmitter 2300 to be reconfigured to use a differentcluster encoding, a reduced number of burst generators, and/or a reducednumber of time slots. This enables transmitter 2300 to adapt tointerference, for example, by avoiding use of the frequency bandssubject to interference, or to provide different data rates at differenttimes or under different conditions.

Controller 2350 in FIG. 68 is preferably implemented as a finite statemachine using combinational logic gates and state registers, but othermeans known in the art, such as a processor and memory, are equallyapplicable.

FIG. 69 shows a control flow diagram for controller 2350 in FIG. 68. Atblock 2360, the controller waits for the enable input to be asserted.Once it is asserted, control advances to block 23700, where thecontroller asserts the start output. After one clock cycle, controller2350 deasserts the start output at block 2380 and continues at block2390. There, the controller waits until time slot counter 2330 assertsits done output, indicating the cluster has been transmitted. Once doneis asserted, controller 2350 continues at block 2360 waiting for thenext data item to transmit.

Referring to FIG. 11, signal decoder 1100 comprises detector captureregisters 1110 a through 1110 n, a start of cluster detector 1120, acontroller 1130, shift registers 1140 a through 1140 n, and a decoder1150. The burst detectors 530 a through 530 n in FIG. 64 sense thecommunication channel and detect frequency bursts in their respectivedetector band. They present the state of the channels on their outputs,which are coupled to the detector capture registers 1110 a through 1110n in FIG. 11. The detector capture registers are implemented as one shotregisters and are set the first time the attached burst detectors sensea frequency burst. They are reset by controller 1130. When activated bythe controller, the shift registers 1140 a through 1140 n capture thestate of the detector capture registers 1110 a through 1110 n duringeach time slot. Simultaneously, they present the captured states (d_(aa)through d_(pn)) to decoder 1150. The decoder determines the receivedsymbol given the detector states d_(aa) through d_(pn) as inputs.Controller 1130 generates the time slot clock, signals the decoding of adata value to the consumer of the received data, and clears the detectorcapture registers prior to receiving the next symbol.

Reception begins when one of the burst detectors 2130 a through 2130 nsenses a frequency burst in its respective band, causing the output ofthe detector capture register (one of 1110 a through 1110 n) connectedto the burst detector to go high. This causes the output of the start ofcluster detector 1120 to go high, enabling the shifting of serial inputdata into the shift registers 1140 a through 1140 n. It also triggersthe controller 1130, which then provides the shift registers with a timeslot clock for the duration of the cluster (p cycles). At the end of acluster, controller 1130 resets the detector state registers, stoppingfurther shifting of the detector state into the shift register and stopsthe time slot clock. The outputs of shift registers 1140 a through 1140n are presented to decoder 1150, which, based on this input, determinesthe received symbol and presents it on the decoder outputs x_(a) throughx_(m). Controller 1130 asserts the valid signal output in parallel withthe decoder output to indicate that a new data value is available. Priorto the reception of the next cluster, controller 1130 resets thedetector state registers to enable reception of another symbol.

The detector capture registers 1110 a through 1110 n are implemented inany way known in the art to be asynchronously set upon a signal by thepulse detectors and to be synchronously or asynchronously reset bycontroller 1130. Examples include RS flip-flops or D flip-flops whoseclock inputs are connected to the pulse detector state output.

Decoder 1150 can be implemented using a RAM, a ROM, or a programmableROM such as an EEPROM addressed by the shift register stage outputs.Alternatively, the decoder can be implemented as a combination of logicgates (combinational logic) whose inputs are the shift register stageoutputs. The number of decoder inputs is generally the number of timeslots p times the number of frequency bands n times the number of bitsprovided by the burst detectors. Preferably, the decoder is implementedsuch that it can be reconfigured at runtime. This enables thetransmitter and receiver subsystems to adapt to interference by changingtheir data encoding, for example, by avoiding bands that containinterfering signals.

Controller 1130 is preferably implemented as a finite state machineusing combinational logic gates and state registers, but other meansknown in the art, such as a processor and memory, are equallyapplicable.

FIG. 71 shows a control flow diagram for controller 1130. At block 1200,the controller initializes itself and then advances to block 1210.There, it waits for the start of cluster detector to indicate anincoming cluster. When an incoming cluster is detected, the controlleradvances to block 1220. There, it initializes the time slot counter tothe number of time slots p and then enters into block 1230. At block1230, the controller tests if the time slot counter has completedcounting the number of slots of one cluster, and, if so, advances tostate 1250. Otherwise, the controller decrements the time slot counterin block 1240, provides a clock pulse to the shift registers andreenters block 1230. At block 1250, the controller asserts the validsignal 1170 for one clock cycle to indicate that a complete cluster hasbeen received and its decoded data value is present on the output ofdecoder 1150. The controller then proceeds to block 1260, where itinitializes a delay counter. In block 1470, the counter is compared tozero to determine if the delay time has been reached. The delay lengthcorresponds to about the interval between successive clusters minus thelength of a cluster and serves to prevent early triggering due tointerference. If the counter has not yet reached zero, it is decrementedin block 1290 before reentering block 1270. When the counter reacheszero, the controller resets the detector capture registers 1110 athrough 1110 n in block 1280 to prepare for the arrival of the nextcluster.

The serial-to-parallel shift registers 1140 a through 1140 n areimplemented as known in the art. FIG. 72 shows a common implementation.The shift register 1300 consists of p D flip-flops connected in series.The input of the leftmost flip-flop is connected to the output of thedetector capture register. The shift input connected to the output ofthe start of cluster detector 1120 causes data to be shifted in whencontroller 1130 provides the time slot clock. The outputs of the shiftregister are connected to decoder 1150. The number of shift registerstages and the number of bits varies with the chosen symbol encoding andthe number of pulse detectors as well as the number of outputs providedby the burst detectors. For example, the burst detectors may provideamplitude information stored in multiple bits instead of a single bitindicating presence or absence of a burst.

Controller 1130 is preferably implemented as a finite state machineusing combinational logic gates and state registers, but other meansknown in the art, such as a processor and memory, are equallyapplicable.

FIG. 73 shows an alternative embodiment of signal decoder 1100 shown inFIG. 70. Signal decoder 1400 comprises detector capture registers 1410 athrough 1410 n, a start of cluster detector 1420, a controller 1430,shift registers 1440 a through 1440 n and a decoder 1450. Burstdetectors 2130 a through 2130 n in FIG. 64 sense the communicationchannel and detect frequency bursts in their respective frequency bands.The burst detectors present the state of the channels on their outputs,which are coupled to the serial inputs of shift registers 1440 a through1440 n and also to the inputs of detector capture registers 1410 athrough 1410 n in FIG. 73. The detector capture registers areimplemented as one shot registers and are set the first time theattached burst detectors sense a frequency burst. They are reset bycontroller 1430. When activated by the controller by providing clockpulses, the shift registers 1440 a through 1440 n capture the state ofthe burst detectors 2130 a through 2130 n shown in FIG. 64 during eachtime slot. Simultaneously, they present the captured states (d_(aa)through d_(pn)) to decoder 1450 by means of the parallel outputs of theshift registers. The decoder determines the received symbol given thedetector states d_(aa) through d_(pn) as inputs. Controller 1430generates the time slot clock, signals the decoding of a data value tothe consumer of the received data, and clears the detector captureregisters prior to receiving the next symbol.

Reception begins when one of the burst detectors 2130 a through 2130 nsenses a frequency burst in its respective band, causing the output ofthe detector capture register (one of 1410 a through 1410 n) connectedto the burst detector to go high. This causes the output of the start ofcluster detector 1420 to go high, enabling the shifting of serial inputdata into the shift registers 1440 a through 1440 n. It also triggersthe controller 1430, which then provides the shift registers with a timeslot clock for the duration of the cluster (p cycles). At the end of acluster, controller 1430 resets the detector state registers, stoppingfurther shifting of the detector state into the shift register and stopsthe time slot clock. The outputs of shift registers 1440 a through 1440n are presented to decoder 1450, which, based on this input, determinesthe received symbol and presents it on the decoder outputs x_(a) throughx_(m). Controller 1430 asserts the valid signal output in parallel withthe decoder output to indicate that a new data value is available. Priorto the reception of the next cluster, controller 1430 resets thedetector state registers to enable reception of another symbol.

Whereas the embodiment of signal detector 1100 shown in FIG. 70 onlydetects the first occurrence of a burst in frequency band, signaldetector 1400 captures the state of the burst detector during each timeslot, thus enabling a broader range of cluster encodings to be used, forexample, a cluster encoding scheme where more than 1 burst per/clusteris transmitted in a given frequency band.

The foregoing presentation of the described embodiments is provided toenable any person skilled in the art to make or use the invention asclaimed. Various modifications to these embodiments are possible, andthe generic principles presented herein may be applied to otherembodiments as well. For example, implementations of a receiver asdescribed herein may also be applied to receive signals transmittedusing chirping techniques as described herein. Modulation techniques andimplementation principles as described herein may be applied tocommunications over wired, wireless (e.g. guided and/or free space),and/or optical (e.g. guided (for example, in a fiber) and/or free space)transmission channels, at frequencies including but not limited to radiofrequency, microwave, millimeter-wave, and optical.

It is further noted that although many of the embodiments describedherein are in the context of a multi-band system transmitting andreceiving wideband and/or ultra-wideband signaling in multiple widebandand/or ultra-wideband frequency bands, the methods and correspondingapparatus presented herein may be implemented in systems usingnarrowband signaling. For example, systems using signaling in which thebandwidth of the multiple frequency bands is less than 2%, typicallysignificantly less than 2% of the center frequency of the respectivefrequency band.

The invention may be implemented in part or in whole as a hard-wiredcircuit and/or as a circuit configuration fabricated into anapplication-specific integrated circuit. The invention may also beimplemented in part or in whole as a firmware program loaded intonon-volatile storage (e.g. ROM or flash or battery-backup RAM) or asoftware program loaded from or into a data storage medium (for example,a read-only or rewritable medium such as a semiconductor orferromagnetic memory (e.g. ROM, programmable ROM, dynamic RAM, staticRAM, or flash RAM); or a magnetic, optical, or phase-change medium (e.g.a floppy, hard, or CD or DVD disk)) as machine-readable code, such codebeing instructions executable by an array of logic elements such as amicroprocessor or other digital signal processing unit or an FPGA.

In some cases, for example, the design architecture for a time divisionmultiple frequency (TDMF) modulation technique according to anembodiment of the invention may be realized in an integrated circuitdevice, such as an application-specific integrated circuit (ASIC). Sucha design may be implemented as a stand-alone packaged device, orembedded as a core in a larger system ASIC. Features of an architectureaccording to certain such embodiments of the invention lend themselveswell to an ASIC implementation that enables low cost, low power, and/orhigh volume production. Embodiments of the invention may include designsthat are scalable with evolving semiconductor technologies, enablingincreased performance objectives and expanded applications. In somecases an entire such architecture may be implemented in a singlesemiconductor process, although even in these cases it may be possibleto transfer the design to multiple semiconductor technologies ratherthan to depend on a single semiconductor process.

Thus, the present invention is not intended to be limited to theembodiments shown above but rather is to be accorded the widest scopeconsistent with the principles and novel features disclosed in anyfashion herein.

What is claimed is:
 1. A method of data transmission, said methodcomprising: encoding, using an encoder, a plurality of data values intoa symbol; transmitting a plurality of bursts using a transmitter, eachburst occupying one of a plurality of frequency bands; wherein at leastan order of transmission of the plurality of bursts in time and apolarity of at least one of the plurality of bursts defines the symbol,the symbol corresponding to the plurality of data values; wherein abandwidth of at least one of the plurality of bursts is at least twopercent of a center frequency of the burst; wherein said plurality ofbursts includes a first burst occupying one of the plurality offrequency bands and a second burst occupying a different one of theplurality of frequency bands, and wherein at least one frequency pointexists at which the amplitude of the first burst is within twentydecibels of a maximum amplitude of the first burst and at which theamplitude of the second burst is within twenty decibels of a maximumamplitude of the second burst.
 2. The method of claim 1, wherein atleast one of the plurality of bursts corresponds to the plurality of thedata values.
 3. The method of claim 1, wherein a duration of at leastone of the plurality of bursts is less than ten cycles.
 4. The method ofclaim 1, wherein the transmitting step comprises: transmitting each ofthe plurality of bursts using the transmitter during one of a series oftime periods, wherein each of the series of time periods has a differentstart time, and wherein during each time period, no more than one of theplurality of bursts is launched.
 5. The method of claim 1 wherein thetransmitting step comprises transmitting the plurality of bursts usingthe transmitter, where the polarity of each burst is modulated on aburst by burst basis according to the symbol.
 6. The method of claim 1wherein the transmitting step comprises transmitting the plurality ofbursts using the transmitter, where the polarity of each burst of theplurality of bursts is modulated to have a same polarity.
 7. The methodof claim 1 wherein the transmitting step comprises transmitting theplurality of bursts using the transmitter, wherein the polarity of agiven one of the plurality of bursts is modulated to be dependent uponthe polarity of another one of the plurality of bursts.
 8. A transmittercomprising: an encoder configured to receive a plurality of data valuesand encode the plurality of data values into a symbol; a signalgenerator configured to transmit a plurality of bursts, each burstoccupying at least one of a plurality of frequency bands, wherein atleast an order of transmission of the plurality of bursts in time and apolarity of at least one of the plurality of bursts defines the symbol,the symbol corresponding to the plurality of data values; and wherein abandwidth of at least one of the plurality of bursts is at least twopercent of a center frequency of the burst; wherein said signalgenerator includes a plurality of burst generators, wherein each of theplurality of burst generators is configured to receive a trigger eventand to generate at least one of the plurality of bursts according to thetrigger event, and wherein at least one of the plurality of burstgenerators is configured to modulate a polarity of at least one of theplurality of bursts.
 9. The transmitter of claim 8, said transmitterfurther comprising a signal launcher configured to receive the pluralityof bursts and to transmit the plurality of bursts over a transmissionmedium.
 10. The transmitter of claim 8, wherein said signal generatorincludes an oscillator configured to output a signal over a selectableone of at least two of the plurality of frequency bands, and whereinsaid signal generator is configured to modulate a polarity of at leastone of the plurality of bursts.
 11. The transmitter of claim 8, whereinthe signal generator is configured to transmit each of the plurality ofbursts during one of a series of time periods, wherein each of theseries of time periods has a different start time, and wherein duringeach time period, no more than one of the plurality of bursts islaunched.
 12. The transmitter of claim 8, wherein the signal generatoris configured to transmit the plurality of bursts, where the polarity ofeach burst is modulated on a burst by burst basis according to thesymbol.
 13. The transmitter of claim 8, wherein the signal generator isconfigured to transmit the plurality of bursts, where the polarity ofeach burst of the plurality of bursts is modulated to have a samepolarity.
 14. The transmitter of claim 8, wherein the signal generatoris configured to transmit the plurality of bursts, wherein the polarityof a given one of the plurality of bursts is modulated to be dependentupon the polarity of another one of the plurality of bursts.
 15. Themethod of claim 1, wherein the transmitting step comprises: transmittingeach of the plurality of bursts using the transmitter during one of aseries of time periods.
 16. The method of claim 1, wherein thetransmitting step comprises: transmitting each of the plurality ofbursts using the transmitter during one of a series of time periods,wherein each of the series of time periods has a different start time.17. A method of data transmission, said method comprising: encoding,using an encoder, a plurality of data values into a symbol; transmittinga plurality of bursts using a transmitter, each burst occupying one of aplurality of frequency bands; wherein at least an order of transmissionof the plurality of bursts in time and a polarity of at least one of theplurality of bursts defines the symbol, the symbol corresponding to theplurality of data values; and wherein a bandwidth of at least one of theplurality of bursts is at least two percent of a center frequency of theburst; wherein the transmitting step comprises: transmitting each of theplurality of bursts using the transmitter during one of a series of timeperiods, wherein each of the series of time periods has a differentstart time, and wherein during at least one time period, more than oneof the plurality of bursts is launched.
 18. The method of claim 17wherein at least the order of transmission of the plurality of bursts intime, a frequency band of at least one of the plurality of bursts andthe polarity of at least one of the plurality of bursts defines thesymbol, the symbol corresponding to the plurality of data values. 19.The method of claim 17 wherein the transmitting step comprises:transmitting the plurality of bursts using the transmitter, each burstoccupying one of the plurality of frequency bands, wherein at least twoof the frequency bands are occupied with at least one of the pluralityof bursts.
 20. The method of claim 17 wherein the symbol corresponds tothe plurality of data values, and the plurality of data values are datato be transmitted from a first device coupled to the transmitter to asecond device coupled to a receiver configured to receive thetransmitted plurality of bursts.